CA2153245C - Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation - Google Patents
Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillationInfo
- Publication number
- CA2153245C CA2153245C CA002153245A CA2153245A CA2153245C CA 2153245 C CA2153245 C CA 2153245C CA 002153245 A CA002153245 A CA 002153245A CA 2153245 A CA2153245 A CA 2153245A CA 2153245 C CA2153245 C CA 2153245C
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- CA
- Canada
- Prior art keywords
- detection
- detected
- criteria
- therapies
- defining
- Prior art date
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/372—Arrangements in connection with the implantation of stimulators
- A61N1/37211—Means for communicating with stimulators
- A61N1/37252—Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
- A61N1/39—Heart defibrillators
- A61N1/3956—Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
- A61N1/3962—Implantable devices for applying electric shocks to the heart, e.g. for cardioversion in combination with another heart therapy
- A61N1/39622—Pacing therapy
Abstract
An implantable antitachyarrhythmia device having the capability of detecting multiple tachyarrhythmias, such as ventricular tachycardia and ventricular fibrillation and capable of delivering multiple therapies, such as antitachycardia pacing, cardioversion and defibrillation. In order to assist the physician in understanding the progress of the device toward detecting a tachyarrhythmia and to better understand the operation of the therapy provided by the device, the device transmits information related to these functions on a beat by beat basis, as a supplement to marker signals associated with paced and sensed heart events. The information telemetry regarding detection allows the physician to determine how the particular R-R interval preceding the telemetry has effected the internal counts or other diagnostic parameters required to accomplish tachyarrhythmia detection. Similarly, in conjunction with stimulus pulses, the device transmits information indicative of which of the available therapy regimens is presently in effect.
Description
WO 94/16764 21 5 3 2 ~ ~ PCT/US93/12222 DIAGNOSTIC TF'.T F.~.TRY SYSTEM FOR AN APPARATUS FOR
DETECTION AND TREATMENT OF TACHYCARDIA AND FIBRILLATION
B~ pro,.l--l of the Invention This invention relates to imp!~nt~ble devices which detect and/or treat S ta:Ly~ll ylh llias and more specific~lly to telemetry systems employed in such devices to ~ ~il ;..ro~ ;on to an external recei~er to assist the physician in ..lo..;to~ g and lm~ in~ the operation of the devices.
In pacem~l~er/cardioverter/defibrill~tors presently in clinir~l evaluation, ventricular fibrill~tion and ventricular ta- h~ardias are identified using rate based criteria In such devices, it is common to specify rate or interval ranges that characterize one or more types of ventricular tachycardias and fibrillation. Counts of the mP~ ed R-R intervals which fall into the rate ranges are used to determine whether a ta~11y~lhr~ ia is present and to ~ ~ose the particular ta~1,y~lhylhmia.
The detection methodolo~ies pr~cticed in such devices may be .liffic~llt for thephysician to follow, as the individual intervals may increment or not increment an individual count ~ on factors other than the interval duration alone. For eY~mrle, rapid onset criteria based on precedin~ intervals may be required to initi~te co~ and stability criteria based on the prece~ intervals may be required to co.~ -le co~ In some devices, whether a me~cll~d R R interval incrementc a count and which count is i.l.;lell.P-Ile~l may be a ~mction of both the individual interval duration and the average rate over the prece(li~ series of intervals. Patents ali~e of such dptectinn metho~lologies in~ lude U.S. Patent No. 4,830,006, U.S.
Patent No. 4,969,465 and U.S. Patent No. 5,063,928.
In impl~nt~ble anti-tachyarrhythmia devices, each of the possible ~ ~oses provided by the device will trigger a prede-fined therapy, with the general ag~essi~el,ess of the therapies increasing from least agglcs~ive if the di~gnosic is a ~ slow ventricular tachycardia to most ag~essive if the di~grocis is ventricular fibrill~tion For eY~mrle, anti-tachycardia pacing may be employed in response toa di~osic of slow ventricular tachycardia, cardioversion may be employed if the WO 94tl6764 215 3 ~ ~ ~ PCTtUS9311222' gn~cic iS fast ventricular tachycardia and defibrill~tion may be employed if the gnQcic iS fibr~ gtion Most ~;u~ tly available devices of the type in which the present invention may be practiced provide for a menu of available therapies for each type of tac~ lhmia (~ nose~ In pro~ g such devices it is typical to specify a number of different therapies for each ~i~gnosed tacll~r~lllyl~ll~ia~ with therapies attempted se~enti~lly in response to the failure of a previous therapy to terminate the arrhythmia. The sequence of therapies actually delivered in such devices mayalso be ~liffi~llt for the physician to follow, as the se~ n~e may depend not only on the particular a"l~ ,ia presently ~ gnosed, but on the success or failure of prece-ling therapies delivered in res~,o"se to previously detected arrhythmias andtor on whether the rhythm has accelerated or decelerated during delivery of a preceding therapy. Patenls illusllaling such therapy delivery srhedllles and menus inrhlde U.S.
Patent No. 4,830,006, U.S. Patent No. 4,969,465 and U.S. Patent No. 5,063,928, referred to above.
Presently available imrl~nt~ble anti-tacl,y~,l"~lh ia devices typically also inrlllde provision for storage of di~nQstic inft~ t;on such as the nurnbers and types of arrhythmias ~1~tected and of the therapies delivered. Some devices, such as the Medtronic Model 7216 and 7217 implantable p~cem~ker/cardioverter/
ll~fihr~ tors also have the c~p~hility to ~,ans,lul marker ch~nnel information in conjllnrtion with each sensed R-wave. This i~o.",a~ion may indicate which interval range the interval ending with the sensed R-wave falls into, based on the ~og~"",rd criteria for idel,liÇying the various tach~ c Other devices inrlllfle the ability to store and l,~ segments of recorded ECG associated with the detection of ~h~rllllllias and/or the delivery of anti-tachyarrhythmia therapies.
Patents ~ closing such ~ n~)stic telemetry systems incl~lde U.S. Patent No.
4,295,474, U.S. Patent No. 4,223,678 and U.S. Patent No. 4,567,883.
Recently, a new telemetry format for implantable devices has been developed, which allows for ll~ ...;s~;on of analog and digital i~o",lation in more compactform, as di~rlosed in U.S. Patent No. 5,127,404, issued to Wyborny et al., 2 ~ 4 5 incorporated herein by reference in its entirety. This telemetry format employs pulse position modulation to encode data in hexadecimal form rather than binary form, dramatically reducing the time required to transmit substantial blocks of information.
Summary of the Invention The present invention provides a telemetry system which assists the physician in following the operation of an implantable anti-tachycardia device, both during detection of tachyarrhythmias and during delivery of anti-tachyarrhythmia therapies. This result is accomplished by transmitting supplemental information with regard to the device's current arrhythmia detection and anti-tachycardia therapy delivery status on a beat by beat basis, following individual detected R-waves or delivered therapy pulses. In the preferred embod-iment of the invention, the status information is transmitted as a supplement to transmission of markers as discussed above, indicating the type of interval ending with the R-wave sensed.
In the disclosed embodiment of the invention, the arrhythmia detection criteria correspond to those disclosed in Canadian Patent Application 2,153,338, by Keimel for a "Method and Apparatus for Detection and Treatment of Tachycardia and Fibrillation", by Keimel et al. The therapy schedule and therapy menu correspond generally to those of the Medtronic Model 7216 and 7217 implantable pacemaker/cardioverter/
defibrillators and the transmission of the status data is accomplished using the improved telemetry format disclosed in A
4 ~ ~ ~3 245 the above-cited Wyborny et al. patent. However, the invention is believed to generally be practicable in conjunction with any devices of the types disclosed in the above cited references.
In accordance with the present invention there is provided an implantable device, comprising: means for detecting heart depolarizations; means for measuring a parameter associated with said detected depolarizations; means for detecting an arrhythmia, said detecting means comprising means for defining criteria for detection of said arrhythmia as a function of said measured parameter, over a series of said detected depolarizations, including means for storing an indication of the relative progress toward said meeting said criteria and for updating said stored information following detected ones of said depolarization; and means for tele-metering information following individual ones of said detected depolarizations to an external receiver, said information comprising said updated stored information as to the relative progress toward meeting said criteria.
Brief Description of the Drawinqs The above and still further objects, features and advantages of the present invention will become apparent from the following detailed description of a presently preferred embodiment, taken in conjunction with the accompanying drawings, and, in which:
Figure 1 is a simplified block diagram illustrating the components of a device within which the method and ~ A
~ ~ 5~ 245 i~
apparatus of the present invention may be implemented.
Figure 2 is a diagram illustrating the format of the telemetry transmissions according to the present invention.
Figure 3 is a block diagram of that portion of the device illustrated in Figure 1 which provides telemetry transmissions according to the present invention.
Figures 4a, 4b, 4c, 4d, 4e, 4f and 4g are tables listing the diagnostic parameters which are telemetered using the present invention.
Detailed Description of the Preferred Embodiment Figure 1 is a functional schematic diagram of an implantable pacemaker/cardioverter/defibrillator in which the present invention may usefully be practiced. This diagram should be taken as exemplary of the type of device in which the invention may be embodied, and not as limiting, as it is believed that the invention may usefully be practiced in a wide variety of device implementations, including devices having functional organization similar to any of the implantable pacemaker/defibrillator/cardioverters presently being implanted for clinical evaluation in the United States.
The invention is also believed practicable in conjunction with implantable pacemaker/cardioverters/defibrillators as disclosed in prior u.S. Patent No. 4,548,209, issued to Wielders, et al. on October 22, 1985, U.S. Patent No.
4,693,253, issued to Adams et al. on September 15, 1987, U.S.
Patent No. 4,830,006, issued to Haluska et al. on May 6, 1989 and U.S. Patent No. 4,949,730, issued to Pless et al. on A
~ ~ ~3 ~
August 21, 1990.
The device is illustrated as being provided with six electrodes, 500, 502, 504, 506, 508 and 510. Electrodes 500 and 502 may be a pair of endocardial electrodes located in the ventricle, mounted to a transvenous lead. Electrode 504 may be located on or may be part of the housing of the implantable pacemaker/cardioverter/defibrillator. Electrodes 506, 508 and 510 may be large surface area defibrillation electrodes located in the ventricle, coronary sinus, superior vena cava or may be subcutaneous or epicardial defibrillation electrodes.
Electrodes 500 and 502 are shown as hard-wired to the inputs and outputs of pacing circuitry 520, which provides bradycardia pacing and anti-tachycardia pacing therapies under control of microprocessor 102 via multi-bit data/address bus 106. The operation of the pacing circuitry may correspond to that described in U.S Patent No. 5,177,824, issued to Keimel et al., U.S Patent No. 5,163,427 issued to Keimel, and U.S.
Patent No. 5,118,105, February 23, 1993 by Keimel.
The pacer circuitry 520 includes a sense amplifier and a pacing pulse generator. Pacing circuitry 520 also includes programmable digital counters which control the basic time intervals associated with bradycardia and anti-tachy-cardia pacing, including the pacing escape intervals, the blanking interval during which the sense amplifier is inactive, the refractory periods during which sensed R-waves are ineffective to restart timing of the pacing escape intervals and widths of the pacing pulses. The durations of A
~ ~ ~3 ~
.
6a these intervals are determined by microprocessor 102, and are communicated to the pacing circuitry 520 via bus 106.
Pacer timing/control circuitry also determines the amplitude of the cardiac pacing pulses, under control of microprocessor 102.
During W I mode pacing, the escape interval counter within pacer circuitry 520 is reset upon sensing of an R-wave on electrodes 500, 502, outside of the refractory period and on timeout triggers generation of a pacing pulse, which is delivered via electrodes 500 and 502. The escape interval counter is also reset on generation of a pacing pulse. The value of the count present in the escape interval counter when reset by sensed R-waves is used to measure the duration of R-R
intervals.
Switch matrix 512 is used to select which of the available electrodes are coupled to band pass amplifier 534.
Selection of which two electrodes are so coupled is controlled by the microprocessor 102 via bus 106. Signals from the selected electrodes are passed through band-pass amplifier 534 20 and into multiplexer 532, where they are converted to multi-bit digital signals by A/D converter 108, for storage in random access memory 104 under control of direct memory address circuit 114. Preferably, a portion of random access memory 104 is configured as a looping or buffer memory which stores at least the preceding several seconds of the EGM
signal. The data stored in the buffer memory may be optionally employed to perform R-wave width measurements as disclosed in A
~ 9 ~ 245 z( 6b U.S. Patent No. 5,312,441, May 17, 1994, by Mader et al, and/or to perform the ventricular fibrillation/ventricular tachycardia discrimination function disclosed in U.S. Patent No. 5,193,535, March 16, 1993 by Bardy et al. However, the present invention may also readily be practiced in devices which do not include such functions.
Microprocessor 102 operates as an interrupt driven device, and responds to interrupts from pacer circuitry 520 corresponding to the occurrence of sensed R-waves and corresponding to the generation of cardiac pacing pulses.
These interrupts are provided via data/address bus 106. Any necessary mathematical calculations to be performed by microprocessor 102 and any updating of the values or intervals controlled by pacer circuitry 520 take place following such interrupts, during the blanking intervals thereafter.
The occurrence of an R-wave is communicated to microprocessor 102 by pacing circuitry 520, via bus 106, and microprocessor 102 notes the time of its occurrence. If the width measurement function is activated, microprocessor 102 waits 100 milliseconds or other physician selected interval following the occurrence of the R-wave detect signal from the pacing circuitry 520, and thereafter transfers the most recent 200 milliseconds or other physician selected interval of digitized EGM stored in the looping or buffer memory portion of the random access memory circuit 104 to a second memory location, where the contents may be digitally analyzed to determine the width of the stored R-wave or to perform the ~4~
2 ~ ~ 3 ~ 4 5 ~
6c tachycardia/fibrillation discrimination function referred to above.
The width measurement function is intended to discriminate between high rate sinus rhythms and ventricular tachycardias, and is preferably only applied to R-waves A' WO 94/16764 ~i~ PCTIUS93/12222 that define the endpoint of an R-R interval within the interval range indicative of ~cl~cal lia and below the interval range indicative of fibrill~tio~ Either as a criterion for initial detection of tachycardia, or after final detection of low rate tachycardia, the device determines whether a predetermined number or proportion S of a series of prece~ R-waves, the widths of which have been me~c~lred, are greater than a preset threshold value (e.g. 8 of the prece~in~ 12 m~cllred R-waves).
If the width criterion is s~ticfie~) initial detection of tacl~car.lia or final detection of slow vçntlicvl~r tacl~cardia is verified. If the criterion is not met, the rhythm is noserl as rapid sinus ~ and no therapy is delivered.
Similar to the width me~Clirclllent fmCtion~ if the discl;~ tor function is activated, microprocessor 102 waits 100 milliseconds or other physician selectedinterval following the oc-;ullellce of the R-wave detect signal, and thereafter transfers the most recent 200 millicecQn~lC or other physician selecte~ interval of rligiti7ed EGM stored in the looping or buffer lllellloly portion of the random access memory circuit 102 to a second memory loc~tion, where the contentc may be digitally analyzed. The microproceCcor 102 identifiec the points in time at which the R-wave detect signal occurs and the point in time at which the 200 ms of stored ECG meets a prede~el~illcd criterion (e.g. peak slope). These two stored times, hereafter ref. ll~d to as the first and second "fir~ l points". The cllmlll~tive variability of the time intervals s~ , the oc~ullence of the first and second fidu~l points over a series of beats is used to .l;~ i$h fibrill~tion from high rate ventricular tacll~lwdia.
The microprocescor 102 also updates counts related to the R-R intervals previously senced The counts are incre-ment~l in rcsl~o~se to m~cllred R-R
intervals falling within associated rate ranges. Presently available a ll,y~llllia control devices, such as the Model 7216 and 7217 p~em~ker/cardioverter/defibrillators available from Medtronic, Inc., employ ~io~;r;1.. ~ble fibrill~tion detection interval ~ ranges and tacl~cardia detection interval ranges which are ~ cent to one another but do not u.ellal). In these Medtronic devices in particular, the interval range - 30 ~Cign~te~l as in-lic~tive of ventricular fibrill~tion (VF) co~ of intervals less than 5 ~
a programmable interval (FDI) and the interval range designated as indicative of ventricular tachycardia (VT) consists of intervals less than a programmable interval (TDI) and greater than or equal to FDI. R-R intervals falling within these ranges are measured and counted to provide a VT event count (VTEC) of R-R intervals falling within the tachycardia interval range and a VF event count (VFEC) of the number intervals, out of a preceding series of a predetermined number (FEB) of intervals, which fall within the fibrillation interval range. VTEC is incremented in response to R-R
intervals that are greater than or equal to FDI but less than TDI, is reset to zero in response to intervals greater than or equal to TDI and is insensitive to intervals less than FDI.
VTEC iS compared to a programmed value (VTNID) and VFEC is compared to a corresponding programmable value (VFNID). When one of the counts equals the corresponding programmable value, the device diagnoses the presence of the corresponding arrhythmia, i.e. fibrillation or tachycardia and delivers an appropriate therapy, e.g. anti-tachycardia pacing, a cardio-version pulse or a defibrillation pulse. In addition, thephysician may optionally require that the measured R-R
intervals meet a rapid onset criterion (rapid increase in rate) before VTEC can be incremented and can also optionally require that should a rate stability criterion (defined variability over a preceding series of intervals) fail to be met, VTEC will be reset to zero. This detection system has proven effective in distinguishing between fibrillation and A
8a ventricular tachycardia so that appropriate therapies may be delivered. Onset and rate stability criteria are discussed in the article "Onset and Stability for Ventricular Tachyar-rhythmia Detection in an Implantable Pacer-Cardioverter-Defibrillator" by Olson et al., published in Computers in Cardioloqy, October 7-10, 1986, IEEE Computer Society Press, pages 167-170.
It is envisioned that the onset and stability requirements are optional in a device employing the present invention, and preferably are made available as programmable options, which may be deleted by external programmer command.
If included, it is believed preferable that the onset criterion be required to meet prior to initiating counting of VTEC, and that once met, the criterion will remain satisfied wo g4/lC7C4 S3~fs PcT/uss3/l2222 .
until ~etecti~n of tacll~l~dia te~n~ t;on. Thus, onset is not inten~led to be a ~etection criterion required for re-detection of tachycardia, following initial detection.
The width criterion, if used, should also be understood to be useful both in initial cletection of tach~cardia and in re-detection of tacl-~. ~dia. This reflects a ~.c;.u~ ,Lion that following initial detection of ventricular tachycardia, absent a proven return to ~orm~l heart rhythm (telll~iualion detect), subsequent high ventricular rates should be l,.es~ d to be ventricular in origin. The stability criterion and the dis~ ;n~tor function may be ap~rol~liate for use both in initial detection and in re-detecti~n In ~tliti~n to the fibrill~tio~ and tachycardia ~letectio~ criteria ~liccllcced above in connecti~n with the Medtronic Model 7216 and Model 7217. The ~licrlQsedembo~lim~nt of the present invention also inrllldes additional detection criteria.
Initial detection of ta~:l~cardia or fibrill~tion detection may also be ~ccomplished using a comhin~l count of all intervals in~ tive of tacl~caldia or fibrill~tion. This comhine~ count (VFEC + VTEC) is rc.~ cd to a co.. ~ .e~l count threshold (CNID). If VTEC + VFEC is equal or ~atcr than CNID, the device checks to see whether VF~C is at least a predet~....inefl n..n.hcr (e.g. 8). If so, the device checks to determine how many of a number (e.g. 8) of the p;ece~ g intervals are greateror equal to FDI. If at least a predetermined number (e.g. 7) are greater than orequal to FDL tacll~ardia is initially detected, othel~ise ventricular fibrillation is initially ~lçtçcte~l The ~lCCG l;"g ~e~ cd intervals are then ~ e~l as ~lis~lcce~1 below to delelll~ e wh~lller the initial ~ ~oC;c of fibrill~fion or ta~h~r~ardia should be ~mçn~le~l to a ~ ~osic of fast ventricular tac~ dia.
The illustrated embo~lim~-nt of the present invention also ~efines two msll inteIval durations FIDI~ and FIDImjn. F~DIma,~ is an interval less than TDI and greater than FDI. FIDImin is an interval less than FDI. The device also ~efinec a third, overlapping interval range incltt(li~ intervals which are less than and ~ealer than or equal to FIDI~"in, which intervals are taken as indi~ ive of the po~cibility that a fast vent~icular ta l~car-lia is oc~ ;lIg, Both F~I~ and FIDImin are ~IO~ ~ hle values, and may either or both be set equal to FDI.
Following initial detection of tachycardia or fibrillation using, the most recent series of R-R intervals (e.g. the last 8 intervals) are examined to determine how many of the intervals fall within the fast ventricular tachycardia interval range. If at least a predetermined number of intervals (e.g. 7) fall within this range, the rhythm is diagnosed as fast ventricular tachycardia. The number of intervals required to diagnose fast ventricular tachycardia may vary depending on whether ventricular fibrillation or ventricular tachycardia is initially detected. For example the device may require that 7 of the preceding 8 intervals fall within the fast ventricular tachycardia interval range to diagnose fast ventricular tachycardia, if fibrillation is initially detected. Otherwise, ventricular fibrillation would be diagnosed. Conversely, the device may only require that at least 2 of the preceding 8 intervals fall within the fast ventricular tachycardia interval range in order to diagnose fast ventricular tachycardia, if tachycardia is initially detected. Otherwise, slow ventricular tachycardia would be diagnosed.
Other detection methods for recognizing tachycardias are described in U.S. Patent No. 4,726,380 issued to Vollman, U.S. Patent No. 4,880,005, issued to Pless et al, U.S. Patent No. 4,830,006, issued to Haluska et al., U.S. Patent No.
5,063,928, issued to Grevis et al. and U.S. Patent No.
4,969,465, issued to Pless et al., may also be used in conjunction with the present invention, as alternatives to the A 66742-5l0 ~ ~ ~ 3 2 4 ~ ~
detection method disclosed specifically herein. However, other detection criteria may also be measured and employed in conjunction with the present invention.
In the event that a tachyarrhythmia is detected, and an anti-tachyarrhythmia pacing regimen is desired, appropriate timing intervals for controlling generation of anti-tachycardia pacing therapies are loaded from microprocessor 524 into the pacer control circuitry 520, to control the operation of the escape interval counter and to define refractory periods during which detection of an R-wave by the R-wave detection circuitry is ineffective to restart the escape interval counter. Similarly, in the event that generation of a cardioversion or defibrillation pulse is required, microprocessor 102 employs the counters in pacer circuitry 520 to control timing of such cardioversion and defibrillation pulses, as well as timing of associated refractory periods during which sensed R-waves are ineffective to reset the timing circuitry.
In response to the detection of fibrillation or a 20 tachycardia requiring a cardioversion pulse, microprocessor 102 activates cardioversion/defibrillation control circuitry 554, which controls charging of the high voltage capacitor banks 560 via charging circuit 550, under control of high voltage charging lines 552, 553. The voltage on the high voltage capacitor banks may be monitored separately via VCAP
lines 538, 539 which are passed through multiplexer 532, and, in response to reaching the same or different predetermined A
7 ~ ~ 3 ~
values set by microprocessor 102, results in generation of logic signals on CAP FULL lines 542, 543, terminating charging of the capacitor banks. Alternatively, only one capacitor bank may be employed or two capacitor banks may be employed, charged together to the same voltage. Thereafter, the timing of the defibrillation or cardioversion pulse is controlled by pacer circuitry 520. One embodiment of an appropriate system for delivery and synchronization of cardioversion and defib-rillation pulses, and controlling the timing functions related to them is disclosed in more detail in U.S. Patent No.
5,118,105 by Keimel, cited above. However, any known cardioversion or defibrillation pulse generation circuitry is believed usable in conjunction with the present invention. For example, circuitry controlling the timing and generation of cardioversion and defibrillation pulses as disclosed in U.S.
Patent No. 4,384,585, issued to Zipes on May 24, 1983, in U.S.
Patent No. 4,949,719 issued to Pless et al., cited above, and in U.S. Patent No. 4,375,817, issued to Engle et al.
Similarly, known circuitry for controlling the timing and 20 generation of anti-tachycardia pacing pulses as described in U.S. Patent No. 4,577,633, issued to Berkovits et al. on March 25, 1986, U. S . Patent No. 4,880,005, issued to Pless et al. on November 14, 1989, U.S. Patent No. 7,726,380, issued to Vollmann et al. on February 23, 1988 and U.S. Patent No.
4,587,970, issued to Holley et al. on May 13, 1986.
In modern pacemaker/cardioverter/defibrillators, the particular anti-tachycardia and defibrillation therapies are ' - ~
12a programmed into the device ahead of time by the physician, and a menu of therapies is typically provided. For example, on initial detection of tachycardia, an anti-tachycardia pacing therapy may be selected. On re-detection of tachycardia, a more aggressive anti-tachycardia pacing therapy may be scheduled. If repeated attempts at anti-tachycardia pacing therapies fail, a higher level cardioversion pulse therapy may be selected thereafter. Prior art patents illustrating such pre-set therapy menus of anti-tachyarrhythmia therapies include the above-cited U.S. Patent No. 4,830,006, issued to Haluska, et al., U.S. Patent No. 4,727,380 issued to Vollmann et al. and U.S. Patent No. 4,587,970, issued to Holley et al.
The present invention is believed practicable in conjunction with any of the known anti-tachycardia pacing and cardio-version therapies, and it is believed most likely that the invention of the present application will be practiced in conjunction with a device in which the choice and order of delivered therapies is programmable by the physician, as in current implantable pacemaker/cardioverter/defibrillators.
In addition to varying the therapy delivered following a failed attempt to terminate a tachyarrhythmia, it is also known that adjustment of detection criteria may be appropriate. For example, adjustment may comprise reducing the number of intervals required to detect a tachyarrhythmia to allow a more rapid re-detection or by changing the interval ranges to bias detection towards detection of ventricular fibrillation, for example as disclosed in U.S. Patent No.
.~
~. ~.
-12b 4,971,058, issued to Pless et al.
The disclosed embodiment of the present invention also provides the ability to select from a menu of therapies for each type of detected tachyarrhythmia, as discussed above.
The therapy menu includes cardioversion and defib-rillation pulses of selectable amplitudes, as well as burst and ramp anti-tachycardia pacing modes for termination of ventricular tachycardias.
wo 94~16764 2~S
In bur~t pacing a series of ventricular pacing pulses is delivered at pulse intervals eqllal to a perceùtage of the average cycle length of the four R-R intervals prcce~ the point VTEC equals VTNID. If the burst sequence is ineffective in te,...;n~ the ta.l~ dia, a subsequent burst sequence may be delivered, at intervals of a lesser ~.,rce~ e of the average cycle length of the re-detected ta~l~c~dia The physician may pro~zuu the number of pulses per burst, the pcr~-~lage of tac~cardia cycle length, the number of sequences per burst pacing thcla~, the dcclclueuL in yclccnlage of cycle length with each s~lcce~ e burst and the ...;~ ... burst pulse interval. The burst pulses may be delivered in ~lem~n(3 mode or optionally in asyncl~onous mode. Ramp pacing delivers a number of pacingpulses, the first pulse interval being equal to a pcrcenlage of the average cycle length of the four R-R intervals prece~iing the point VTEC equals VTNID, with the interval l~cl._en pulses ~c~ c;..g with each pulse delivered. If the ramp sequence is inPff~ctive in te~ g the tacl~cardia, another ramp sequence may be delivered, with an initial interval of a lesser l.crce-~ e of the average cycle length of the re-detecte~l tacl~cardia and s~lbseq~lç-nt intervals collcslJo~ Iy reduced and with an m. l~,~cd ~ cr of pulses. The physician may yiO~ the n~n~bcr of pulses in the first ramp, the pcr~--~age of ta. l~caldia cycle length for the first interval, the cr of s~q~lenres per ramp pacing lLe~a~/~ the de~lcllle.l~ in ycrce-ol~e of cycle length with each s~lc~ ramp seqUçnre and the ~ --J~ pulse interval . The pulses may be delivered in dÇm~nd mode or optionally in a~llcllrollous mode.
Each ~1etçcte~ h~ia (slow VT, fast VT, fibrill~tion) may have, for cA~le, up to six s~ate thela~ies ~ro~ed for use seq~le.nti~lly, each delivered in rcsl,~,~c to the previously delivered therapy failing to telll i late the detectecl a,l~ia For ~ ~lc, slow VT might have two ramp pacing therapies ~rogl~.. c~l followed by two burst pacing Illela~ics. Fast VT might have ~nly one ramp pacing therapy, followed by one burst ~ela~, and then by cardioversion pulses of in~;lca~ m~ de FibAllation will typic~lly have four defibAllation pulse ~elapies of in~;leasing ~n~r~ de In the present invention, selection of the partic-ular electrode configuration for delivery of the cardioversion or defibrillation pulses is controlled via output circuit 548, under control of cardioversion/defibrillation control circuitry 554 via control bus 546. Output circuit 548 determines which of the high voltage electrodes 506, 508 and 510 will be employed in delivering the defibrillation or cardioversion pulse regimen, and may also be used to specify a multi-electrode, simultaneous pulse regimen or a multi-electrode sequential pulse regimen. Monophasic or biphasicpulses may be generated. One example of circuitry which may be used to perform this function is set forth in commonly assigned U.S. Patent No. 5,163,427, cited above. However, output control circuitry as disclosed in U.S. Patent No.
4,953,551, issued to Mehra et al. on September 4, 1990 or U.S.
Patent No. 4,800,883, issued to Winstrom on January 31, 1989 may also be used in the context of the present invention.
Alternatively single monophasic pulse regimens employing only a single electrode pair according to any of the above cited references which disclose implantable cardioverters or defibrillators may also be used.
The telemetry circuitry employed to practice the present invention in the device illustrated in Figure 1 includes telemetry timing/control circuitry 121, cyclic redundancy code circuitry 112 and uplink timing circuitry 118.
The operation of these circuit blocks and their inter-connection to the analog to digital converter 108, the A 667425l0 ~ ~ 5 ~
14a address/data bus 106, microprocessor 102, random access memory 104 and direct memory address circuitry 114 is discussed more fully in U.S. Patent No. 5,127,404, issued to Wyborny et al.
and incorporated herein by reference in its entirety. Also employed in the telemetry function are telemetry control circuitry 124, telemetry demodulator 122 and antenna driver 120, which are discussed in more detail below.
Figure 3, corresponding to Figure 4 of the Wyborny et al. patent illustrates the telemetry timing and control circuitry 121 in more detail. Telemetry timing/control circuitry 121 controls the formatting and timing of uplink telemetry, as described in the above cited Wyborny et al.
patent. Digital inputs to telemetry timing/control circuitry 121 are provided on multi-bit bus 106. Analog input to the telemetry A' 66742-510 W094/lC7C4 21$32~S ~IU593/12222 timing/control ~;uilly 121 is provided via analog to digital collve,ler 108, which co~ analog ~ign~1c, such as internal elcc1l0~s via ~mrlifier 534, the voltage of the output c~p~~itors as in~lic~teel on line 538, and other available analog inputs on line 110 such as battery voltage, etc. into digital format for tr~ ~C~ c~ion Both the S output ADC bus from analog to digital COll~Cl ler 108 and the address/data bus 106 are provided to a 12 bit data buffer 116 within telel,letl~ tirning\control ~ ;uih~ 121.
This buffer 116 is divided into two sectionc~ one section 119 sel~ing to store a four bit frame identifier code, the second section 117 SPlvillg to store a four bit upper nibble and a four bit lower nibble, which together make up a single data frame as described in above-cited Wyborny patent. Uplink timing block 118 decodes the 12 bits of data stored in data buffer 116 to produce a set of timing signals which key bursts of RF energy at the a~lol,liate times to pulse position mo~ te a 175 kilohertz carrier. Uplink timing 118 also keys bursts of RF energy at fL~ed position~
within the tC4~ frame col.e~ollding to the frame in;~ g pulse and the ~llcl~o~ ;.. g pulse, as illustrated in Figure 2, Aiccucce~l below. Cyclic re~hlnA~ncy code block 112 is employed to genelate the cyclic re~l----(l~--cy code used to provide fol. ard error ~etection in uplink telem~try~ and, may optionally also be employed for analyzing and ~ ; data received via downlink telemetry.
~el~ ~-;Qg to Figure 1, the output of timing block 118 is provided to telemetIy circuit 124 which, in re~c to receipt of signals from uplink timing block 118 ~ E,e~ the ~ e~ driver 120 to deliver bursts of RF energy to ~ntenn~ 125.
Telçmetfy ~mnA~ tion block 122 A~moAlll~tes pulse interval çn~o~le~l downlink tÇ~emetry reoe;~_d on ~ ç~ 124, and provides to telemetry block 124, which in turn provides the seAally l n~.c...;lle~l digital data rccei~cd via telemetry ~emo~ tor 122 into parallel format to delivery to microproceccor 102 via address/data bus 106.
Figure 2 illustrates the frame format of a telemetry IlA~ ;ccion accordillg to the present invention, and Ctilles~)ollr1s to Figure 2 of the above cited Wyborny et al.
patent. The basic unit of the format is a frame 30, having a duration of T"5. In the Aic~ l~sefl emboAimpntJ the main timing source for ge~l~lion of the telemetry frame ~ 30 col~ ises a st~n~1~rd 32.768 kiloherP crystal clock which provides a basic clock cycle WO 94/lC764 PCT/US93/1222, 21S3~5 . .
of 30.52 microsec~n~lc. Thus, a frame col~lised of 64 clock cydes eYt~Pn~ling over a fixed time interval of 1.953125 milliseconds provides a coll~el.ient frame, as the frame period is a binary multiple of the basic clock cycle. All signals within the frame coL.ll,lise bursts of RF energy, triggered by uplink timing ci~ iLly 118. The first signal is a frame signal 29 which de-finPs the l,c~;.,ni~g of the frame. The second signal is a ~llCll~Q ~ g signal CO~ g a burst 32 which is located at a time TG1 within fra ne 30. The frame identifier code is posifionPcl within the second fixed range of each frarne 30. The ;dentifier code colllplises an ~ Pntifier RF pulse 36 which is pulse position mod~llatetl to one of 16 available locations within the identifi=P-r range 38, and thus is a single bit heY~deçim~l value co~res~ol-ding to the 4 bit frame j~1Pntifier code stored in the first section 119 of data buffer 116 in telemetry timing and control clr~ y 121 (Fig.3). This single hexadecimal bit serves to identify the nature or type of data found within the frame.
Each frame also inrllldes two h~Y~decim~l bits coll-_s~Jo"r~ to the two 4 bit nibbles m~h~ Up the eight bit byte of data stored in the second portion 117 of data buffer 116 in tc~ r timing and control ~h. .~ 121 (Fig. 3). The telemetered data is enroded as two h~Y~ecim~l bits. The first heY~-lecim~l bit colles~ollding to the four least ci~ifi~nt bits of the byte is a pulse 42 positione~ within a third fixed range of frarne 3Q CO~ iug lower nibble range 44. The second hoY~de~m~l bit, c~ sp~ to the four most cierific~nt bits of the data byte is a pulse 46, p~Cisi~ne~ within a fourth fL~ced range of frame 3Q upper nibble range 48. Both the upper and lower nibble ranges inrlllde 16 identifi~ble pulse loc~fionc within the upper and lower nibble ranges 48 and 44, respectively.
The data ide-ntifier may fall within clock cycles 9-19 following the first clockcycle of the data frame, r3~ofinPd by the delivery of the frame pulse 29. As indicted in the below, de~e~ g on which cycle the frame pulse falls, a variety of types of data may be in~lir~te-l Data ~ Pntifier codes in~ de a ~ lber of mP~c~lred analog values inrl~ in~ the present level of VDD (5 Hex), battery voltage me~ l cn'ent (6 Hex) and the di~elel-ce (delta V.) between 1~P~ ;ng and trailing edges of battery voltages (7 Hex), analog EGM (8 Hex), and the voltages on two output capacitor 5 ~
banks (9 and A Hex). In addition, telemetry of programmed parameters (0 Hex) may be identified. Of most importance with regard to the present invention, however, are the marker (2 Hex) and marker supplement (3 Hex) data types.
The present invention, like the Medtronic Model 7216 and 7217 implantable pacemaker/cardioverter/defibrillators includes an extensive set of marker codes to be transmitted in conjunction with sensing of intrinsic depolarizations, and in conjunction with delivery of bradycardia pacing pulses, anti-tachycardia pacing pulses, as well as cardioversion and defib-rillation pulses. These marker codes are listed in the table illustrated in Figure 4a. Figure 4a also includes reserved marker codes for use in conjunction with future devices which may also employ electrodes adapted to sense atrial heart rhythms and also includes marker designations for delivery of atrial anti-tachycardia and defibrillation therapies. On receipt by an external programmer, these marker codes are translated into graphical signals for display in conjunction with a sensed electrocardiogram, as described in U.S. Patent No. 4,374,382, issued to Markowitz et al., describing the basic functioning of marker channel transmissions as presently used in many commercially available pacemakers. Graphic symbols corresponding to the marker codes are illustrated for ventricular events in Fig. 4g. Atrial events could employ the same symbols but with reversed polarity (i.e. extending below the baseline).
,~4 2 ~ 5 3 ~ ~ ~
17a In addition to markers simply designating the type of individual events which occur, the present invention usefully provides marker supplement data, which is uplinked following the marker codes when the pacing interval of the device is greater than or equal to 100 milliseconds. Each block of marker supplement data is transmitted in the form of five sequential frames, each containing one byte of marker supplement information. Available information is formatted into the five marker supplement bytes, as indicted in the tables 4b, 4c, 4d, 4e and 4f, with information listed in order of priority for inclusion as part of a marker supplement transmlsslon.
Figure 4b illustrates the binary codes for the data bits in marker supplement frame one. These 8 bit binary bytes are encoded as two hexadecimal bits for ~ ~, WO 94tl6764 ~ PCTtUS93tl222 ', 21S32~'3 ;on, as ~ se~ above. Supplement data byte one is a general device status byte, broken into four two and one bit subunits. The first two bits are related to the status of the device vis a vis its telemetry operation, the third bit indic~tes whether a tachy~lLylhl,lia episode is in process, the fourth bit indicates whether any previous tacl~ ,ia episodes had been detected since the last time the memory was cleared, and the sixth and seventh bits indicate the ~ nçes under which the VT event connter was most rccel,lly reset.
Figure 4c illustrates marker supplement byte two, in a format co-,e;.~onding to Figure 4b. Byte two, ~ ed in the second marker supplement frame, either provides i~U~ n with regard to the status of the VF event counter or the status of the high voltage output c~p~ritor charging process and the status as to whether one of a llulllber of available therapies is being delivered. Status with regard to the VF event countçr is ~ ed as an alterative to il to.~ation indjc~ting the particular type of lhe~ , esenll~ being delivered, and/or in-lic~ting high voltage c~r~citor cL~g, as the VF event counter is disabled during cha~g and during delivery of anti-tacl~ lhll,ia thelap.cs. As intli~te-l in ~igure 4c, status in~ tors with regard to slow VT, fast VT and VF ~hel~ies are available, with theability to deci~te which of six physician selected therapies for each of these three ta.:l~ll~lh~;a tiia~oses are being delivered. This il.iollllation, in conjunction with i~ru~ t;on with regard to the therapies chosen by the physician, allows for a more con~plete lm~lP-~st~n~ling of the f~lnrtioning of the device.
Figure 4d illu~llates marker supplçm~-nt byte three, in a format colle~ollding to Figure 4b. The third marker supplement byte either in'~ t~PS the status of the VT
event count or the VT therapy scan ll-~ber presently in ylu~e;~s. These data types are ~llc ~t;~res to one another, in that the VT detection operation is disabled during delivery of an anti-tacl~ ~ia therapy. As ~lic~lcsed above in conjunction with the burst and ramp anti-tachycardia pacing therapies, each therapy may be repe~t~l for a llu.-lber of se~lP-nres or scans, before going on to the next therapy. In the event that such a lllela~ is being delivered, the third mark supplement byte will in-lic~te which scan or sequence of the selected therapy is presently being delivered, WO 94/16764 ~ S3~s PCT/US93112222 further enh~nring the physician's underst~n~ling of the therapy being delivered.Conversely, if the device is not delivering a therapy, the VT event count would ~cco...r ~ny a VF event count in marker supplement byte two, providing a more complete underst~nding of the ~roE;less towards tach~llJ~rthmia detectior S Figure 4e illustrates marker supplement byte four, in a format col~e~ollding to Figure 4b. Marker supplement byte four provides a telemetered value of the ~P~ ed R-R interval prece-ling the pacing pulse or sensed ventricular depolqri7~ti~ n, and can be used in conjunrtion with the increm~nted values of the VT and VF event counts, to further refine the physician's underst~n~ling of the detection methodQlogy Figure 4f illustrates marker supplement byte five, in a format collesponding to Figure 4b. Marker supplem~o-nt byte five is a status byte, when the first bit is zero, the re-..A;-~;-.g bits are used to in~ te status of detection and therapy pro~;1----"i"g The second bit ;-~ ec whether VF therapies are IJlo~;~ cd on. the third bit being used to in~ic~te whether fast VT therapies are pl~Og~ ~-"",rd on and the fourth bit being used to in~lir~ted whether slow VT Illela~:es are ~,u~; ~ ..ed on. The fifth bit is employed to in~li~te whether VF ~letectiQn is activated, the sixth, seventh and eighth bits being used to indie~te whether fast VT detection via VF is pro~; ~ ned on, and whether VT detection is l,lo~ .. ed on. With the first bit at 1, the 1~-.-~;.. ;.. ~ bits inrlulle h~rolll~ nn as to ~Leth~r the .. P~ rCd elc~tlu~ll width met the width criterion and, and as to the ...P~ .ed electrogram width.
As devices accordhlg to the present invention lJio~es5, it is ~nti~ip~ted that ~d~lition~l types of marker status h~folmalion will be added, particularly in cQnjnnrtion with devices which sense and treat atrial a~ h...;~c, and as additional detection methodologies and criteria are added. For example, in conjunction witha device as (licclose~ in the present application, additional marker supplement bytes which in~lic~te whether the onset criteria has been satisfied, whether the rate stability criterion has been ~ticfied or whether other tachycardia detection criteria such as the width ~P~ enl and V-T/V-F dis~ or filnctionc described above have been s~ticfied are certainly well within the scope of the present invention. Similarly, marker status bytes indicating the status of detection of atrial arrhythmias and the status of delivery of therapies for treating atrial arrhythmias will be included in devices which have these capabilities.
While the prefe,led embodiment of the device takes the form of a microprocecsor controlled device as illustrated in Figure 1, in which the operation of tbe device is controlled by stored software, the invention may equally well be pr~cticed in the form of a ~lefli~tell~ full c~lctom digital integrated circuit or, even in the form of an analog circuit, employing analog values as substit~ltes for the digital values ~liccl~sed in conj!~n~ n with the above specification.
In ~dditiQn~ while the preferred embo~liment ~iic~lQsed above takes the form of a p~cem~-Pr/cardioverter/ defibrillator, the enh~nce~ ability to telemeter i~ol...~l;on regardillg detection of tachyarrhythmias and delivery of anti-arrhythmia tberapies provided by the present invention are also valuable and applicable to devices which are only capable of pelrolll.il,g a subset of the various therapies ~iccllcce-l above in cQ~ ;Qn with Figure 1.
It should further be kept in mind tbat while the tberapies described for delivery in respQ~e to ~letection of the various ~rlh~rL~iaS ~licc~lcsed are all~liccl~!se~ in the ~u..t~ ~l of electric~l therapies, it is possible that the invention may be embodied in the form of an impl~nt~ble drug dispellser, wherein one or more of the anti-~acl~dia ~el~pies takes the form of injection of a drug locally into the heart or ~le~ ly to treat the detected arrhythmia. As such, the above ~licclos~re should be taken merely as an eY~mple of an embo~limpnt of the present invention,rather than l;..-;L;i~g, when reading the claims which follow.
In co-j,~ ;Qn with the above specific~tion~ I claim:
DETECTION AND TREATMENT OF TACHYCARDIA AND FIBRILLATION
B~ pro,.l--l of the Invention This invention relates to imp!~nt~ble devices which detect and/or treat S ta:Ly~ll ylh llias and more specific~lly to telemetry systems employed in such devices to ~ ~il ;..ro~ ;on to an external recei~er to assist the physician in ..lo..;to~ g and lm~ in~ the operation of the devices.
In pacem~l~er/cardioverter/defibrill~tors presently in clinir~l evaluation, ventricular fibrill~tion and ventricular ta- h~ardias are identified using rate based criteria In such devices, it is common to specify rate or interval ranges that characterize one or more types of ventricular tachycardias and fibrillation. Counts of the mP~ ed R-R intervals which fall into the rate ranges are used to determine whether a ta~11y~lhr~ ia is present and to ~ ~ose the particular ta~1,y~lhylhmia.
The detection methodolo~ies pr~cticed in such devices may be .liffic~llt for thephysician to follow, as the individual intervals may increment or not increment an individual count ~ on factors other than the interval duration alone. For eY~mrle, rapid onset criteria based on precedin~ intervals may be required to initi~te co~ and stability criteria based on the prece~ intervals may be required to co.~ -le co~ In some devices, whether a me~cll~d R R interval incrementc a count and which count is i.l.;lell.P-Ile~l may be a ~mction of both the individual interval duration and the average rate over the prece(li~ series of intervals. Patents ali~e of such dptectinn metho~lologies in~ lude U.S. Patent No. 4,830,006, U.S.
Patent No. 4,969,465 and U.S. Patent No. 5,063,928.
In impl~nt~ble anti-tachyarrhythmia devices, each of the possible ~ ~oses provided by the device will trigger a prede-fined therapy, with the general ag~essi~el,ess of the therapies increasing from least agglcs~ive if the di~gnosic is a ~ slow ventricular tachycardia to most ag~essive if the di~grocis is ventricular fibrill~tion For eY~mrle, anti-tachycardia pacing may be employed in response toa di~osic of slow ventricular tachycardia, cardioversion may be employed if the WO 94tl6764 215 3 ~ ~ ~ PCTtUS9311222' gn~cic iS fast ventricular tachycardia and defibrill~tion may be employed if the gnQcic iS fibr~ gtion Most ~;u~ tly available devices of the type in which the present invention may be practiced provide for a menu of available therapies for each type of tac~ lhmia (~ nose~ In pro~ g such devices it is typical to specify a number of different therapies for each ~i~gnosed tacll~r~lllyl~ll~ia~ with therapies attempted se~enti~lly in response to the failure of a previous therapy to terminate the arrhythmia. The sequence of therapies actually delivered in such devices mayalso be ~liffi~llt for the physician to follow, as the se~ n~e may depend not only on the particular a"l~ ,ia presently ~ gnosed, but on the success or failure of prece-ling therapies delivered in res~,o"se to previously detected arrhythmias andtor on whether the rhythm has accelerated or decelerated during delivery of a preceding therapy. Patenls illusllaling such therapy delivery srhedllles and menus inrhlde U.S.
Patent No. 4,830,006, U.S. Patent No. 4,969,465 and U.S. Patent No. 5,063,928, referred to above.
Presently available imrl~nt~ble anti-tacl,y~,l"~lh ia devices typically also inrlllde provision for storage of di~nQstic inft~ t;on such as the nurnbers and types of arrhythmias ~1~tected and of the therapies delivered. Some devices, such as the Medtronic Model 7216 and 7217 implantable p~cem~ker/cardioverter/
ll~fihr~ tors also have the c~p~hility to ~,ans,lul marker ch~nnel information in conjllnrtion with each sensed R-wave. This i~o.",a~ion may indicate which interval range the interval ending with the sensed R-wave falls into, based on the ~og~"",rd criteria for idel,liÇying the various tach~ c Other devices inrlllfle the ability to store and l,~ segments of recorded ECG associated with the detection of ~h~rllllllias and/or the delivery of anti-tachyarrhythmia therapies.
Patents ~ closing such ~ n~)stic telemetry systems incl~lde U.S. Patent No.
4,295,474, U.S. Patent No. 4,223,678 and U.S. Patent No. 4,567,883.
Recently, a new telemetry format for implantable devices has been developed, which allows for ll~ ...;s~;on of analog and digital i~o",lation in more compactform, as di~rlosed in U.S. Patent No. 5,127,404, issued to Wyborny et al., 2 ~ 4 5 incorporated herein by reference in its entirety. This telemetry format employs pulse position modulation to encode data in hexadecimal form rather than binary form, dramatically reducing the time required to transmit substantial blocks of information.
Summary of the Invention The present invention provides a telemetry system which assists the physician in following the operation of an implantable anti-tachycardia device, both during detection of tachyarrhythmias and during delivery of anti-tachyarrhythmia therapies. This result is accomplished by transmitting supplemental information with regard to the device's current arrhythmia detection and anti-tachycardia therapy delivery status on a beat by beat basis, following individual detected R-waves or delivered therapy pulses. In the preferred embod-iment of the invention, the status information is transmitted as a supplement to transmission of markers as discussed above, indicating the type of interval ending with the R-wave sensed.
In the disclosed embodiment of the invention, the arrhythmia detection criteria correspond to those disclosed in Canadian Patent Application 2,153,338, by Keimel for a "Method and Apparatus for Detection and Treatment of Tachycardia and Fibrillation", by Keimel et al. The therapy schedule and therapy menu correspond generally to those of the Medtronic Model 7216 and 7217 implantable pacemaker/cardioverter/
defibrillators and the transmission of the status data is accomplished using the improved telemetry format disclosed in A
4 ~ ~ ~3 245 the above-cited Wyborny et al. patent. However, the invention is believed to generally be practicable in conjunction with any devices of the types disclosed in the above cited references.
In accordance with the present invention there is provided an implantable device, comprising: means for detecting heart depolarizations; means for measuring a parameter associated with said detected depolarizations; means for detecting an arrhythmia, said detecting means comprising means for defining criteria for detection of said arrhythmia as a function of said measured parameter, over a series of said detected depolarizations, including means for storing an indication of the relative progress toward said meeting said criteria and for updating said stored information following detected ones of said depolarization; and means for tele-metering information following individual ones of said detected depolarizations to an external receiver, said information comprising said updated stored information as to the relative progress toward meeting said criteria.
Brief Description of the Drawinqs The above and still further objects, features and advantages of the present invention will become apparent from the following detailed description of a presently preferred embodiment, taken in conjunction with the accompanying drawings, and, in which:
Figure 1 is a simplified block diagram illustrating the components of a device within which the method and ~ A
~ ~ 5~ 245 i~
apparatus of the present invention may be implemented.
Figure 2 is a diagram illustrating the format of the telemetry transmissions according to the present invention.
Figure 3 is a block diagram of that portion of the device illustrated in Figure 1 which provides telemetry transmissions according to the present invention.
Figures 4a, 4b, 4c, 4d, 4e, 4f and 4g are tables listing the diagnostic parameters which are telemetered using the present invention.
Detailed Description of the Preferred Embodiment Figure 1 is a functional schematic diagram of an implantable pacemaker/cardioverter/defibrillator in which the present invention may usefully be practiced. This diagram should be taken as exemplary of the type of device in which the invention may be embodied, and not as limiting, as it is believed that the invention may usefully be practiced in a wide variety of device implementations, including devices having functional organization similar to any of the implantable pacemaker/defibrillator/cardioverters presently being implanted for clinical evaluation in the United States.
The invention is also believed practicable in conjunction with implantable pacemaker/cardioverters/defibrillators as disclosed in prior u.S. Patent No. 4,548,209, issued to Wielders, et al. on October 22, 1985, U.S. Patent No.
4,693,253, issued to Adams et al. on September 15, 1987, U.S.
Patent No. 4,830,006, issued to Haluska et al. on May 6, 1989 and U.S. Patent No. 4,949,730, issued to Pless et al. on A
~ ~ ~3 ~
August 21, 1990.
The device is illustrated as being provided with six electrodes, 500, 502, 504, 506, 508 and 510. Electrodes 500 and 502 may be a pair of endocardial electrodes located in the ventricle, mounted to a transvenous lead. Electrode 504 may be located on or may be part of the housing of the implantable pacemaker/cardioverter/defibrillator. Electrodes 506, 508 and 510 may be large surface area defibrillation electrodes located in the ventricle, coronary sinus, superior vena cava or may be subcutaneous or epicardial defibrillation electrodes.
Electrodes 500 and 502 are shown as hard-wired to the inputs and outputs of pacing circuitry 520, which provides bradycardia pacing and anti-tachycardia pacing therapies under control of microprocessor 102 via multi-bit data/address bus 106. The operation of the pacing circuitry may correspond to that described in U.S Patent No. 5,177,824, issued to Keimel et al., U.S Patent No. 5,163,427 issued to Keimel, and U.S.
Patent No. 5,118,105, February 23, 1993 by Keimel.
The pacer circuitry 520 includes a sense amplifier and a pacing pulse generator. Pacing circuitry 520 also includes programmable digital counters which control the basic time intervals associated with bradycardia and anti-tachy-cardia pacing, including the pacing escape intervals, the blanking interval during which the sense amplifier is inactive, the refractory periods during which sensed R-waves are ineffective to restart timing of the pacing escape intervals and widths of the pacing pulses. The durations of A
~ ~ ~3 ~
.
6a these intervals are determined by microprocessor 102, and are communicated to the pacing circuitry 520 via bus 106.
Pacer timing/control circuitry also determines the amplitude of the cardiac pacing pulses, under control of microprocessor 102.
During W I mode pacing, the escape interval counter within pacer circuitry 520 is reset upon sensing of an R-wave on electrodes 500, 502, outside of the refractory period and on timeout triggers generation of a pacing pulse, which is delivered via electrodes 500 and 502. The escape interval counter is also reset on generation of a pacing pulse. The value of the count present in the escape interval counter when reset by sensed R-waves is used to measure the duration of R-R
intervals.
Switch matrix 512 is used to select which of the available electrodes are coupled to band pass amplifier 534.
Selection of which two electrodes are so coupled is controlled by the microprocessor 102 via bus 106. Signals from the selected electrodes are passed through band-pass amplifier 534 20 and into multiplexer 532, where they are converted to multi-bit digital signals by A/D converter 108, for storage in random access memory 104 under control of direct memory address circuit 114. Preferably, a portion of random access memory 104 is configured as a looping or buffer memory which stores at least the preceding several seconds of the EGM
signal. The data stored in the buffer memory may be optionally employed to perform R-wave width measurements as disclosed in A
~ 9 ~ 245 z( 6b U.S. Patent No. 5,312,441, May 17, 1994, by Mader et al, and/or to perform the ventricular fibrillation/ventricular tachycardia discrimination function disclosed in U.S. Patent No. 5,193,535, March 16, 1993 by Bardy et al. However, the present invention may also readily be practiced in devices which do not include such functions.
Microprocessor 102 operates as an interrupt driven device, and responds to interrupts from pacer circuitry 520 corresponding to the occurrence of sensed R-waves and corresponding to the generation of cardiac pacing pulses.
These interrupts are provided via data/address bus 106. Any necessary mathematical calculations to be performed by microprocessor 102 and any updating of the values or intervals controlled by pacer circuitry 520 take place following such interrupts, during the blanking intervals thereafter.
The occurrence of an R-wave is communicated to microprocessor 102 by pacing circuitry 520, via bus 106, and microprocessor 102 notes the time of its occurrence. If the width measurement function is activated, microprocessor 102 waits 100 milliseconds or other physician selected interval following the occurrence of the R-wave detect signal from the pacing circuitry 520, and thereafter transfers the most recent 200 milliseconds or other physician selected interval of digitized EGM stored in the looping or buffer memory portion of the random access memory circuit 104 to a second memory location, where the contents may be digitally analyzed to determine the width of the stored R-wave or to perform the ~4~
2 ~ ~ 3 ~ 4 5 ~
6c tachycardia/fibrillation discrimination function referred to above.
The width measurement function is intended to discriminate between high rate sinus rhythms and ventricular tachycardias, and is preferably only applied to R-waves A' WO 94/16764 ~i~ PCTIUS93/12222 that define the endpoint of an R-R interval within the interval range indicative of ~cl~cal lia and below the interval range indicative of fibrill~tio~ Either as a criterion for initial detection of tachycardia, or after final detection of low rate tachycardia, the device determines whether a predetermined number or proportion S of a series of prece~ R-waves, the widths of which have been me~c~lred, are greater than a preset threshold value (e.g. 8 of the prece~in~ 12 m~cllred R-waves).
If the width criterion is s~ticfie~) initial detection of tacl~car.lia or final detection of slow vçntlicvl~r tacl~cardia is verified. If the criterion is not met, the rhythm is noserl as rapid sinus ~ and no therapy is delivered.
Similar to the width me~Clirclllent fmCtion~ if the discl;~ tor function is activated, microprocessor 102 waits 100 milliseconds or other physician selectedinterval following the oc-;ullellce of the R-wave detect signal, and thereafter transfers the most recent 200 millicecQn~lC or other physician selecte~ interval of rligiti7ed EGM stored in the looping or buffer lllellloly portion of the random access memory circuit 102 to a second memory loc~tion, where the contentc may be digitally analyzed. The microproceCcor 102 identifiec the points in time at which the R-wave detect signal occurs and the point in time at which the 200 ms of stored ECG meets a prede~el~illcd criterion (e.g. peak slope). These two stored times, hereafter ref. ll~d to as the first and second "fir~ l points". The cllmlll~tive variability of the time intervals s~ , the oc~ullence of the first and second fidu~l points over a series of beats is used to .l;~ i$h fibrill~tion from high rate ventricular tacll~lwdia.
The microprocescor 102 also updates counts related to the R-R intervals previously senced The counts are incre-ment~l in rcsl~o~se to m~cllred R-R
intervals falling within associated rate ranges. Presently available a ll,y~llllia control devices, such as the Model 7216 and 7217 p~em~ker/cardioverter/defibrillators available from Medtronic, Inc., employ ~io~;r;1.. ~ble fibrill~tion detection interval ~ ranges and tacl~cardia detection interval ranges which are ~ cent to one another but do not u.ellal). In these Medtronic devices in particular, the interval range - 30 ~Cign~te~l as in-lic~tive of ventricular fibrill~tion (VF) co~ of intervals less than 5 ~
a programmable interval (FDI) and the interval range designated as indicative of ventricular tachycardia (VT) consists of intervals less than a programmable interval (TDI) and greater than or equal to FDI. R-R intervals falling within these ranges are measured and counted to provide a VT event count (VTEC) of R-R intervals falling within the tachycardia interval range and a VF event count (VFEC) of the number intervals, out of a preceding series of a predetermined number (FEB) of intervals, which fall within the fibrillation interval range. VTEC is incremented in response to R-R
intervals that are greater than or equal to FDI but less than TDI, is reset to zero in response to intervals greater than or equal to TDI and is insensitive to intervals less than FDI.
VTEC iS compared to a programmed value (VTNID) and VFEC is compared to a corresponding programmable value (VFNID). When one of the counts equals the corresponding programmable value, the device diagnoses the presence of the corresponding arrhythmia, i.e. fibrillation or tachycardia and delivers an appropriate therapy, e.g. anti-tachycardia pacing, a cardio-version pulse or a defibrillation pulse. In addition, thephysician may optionally require that the measured R-R
intervals meet a rapid onset criterion (rapid increase in rate) before VTEC can be incremented and can also optionally require that should a rate stability criterion (defined variability over a preceding series of intervals) fail to be met, VTEC will be reset to zero. This detection system has proven effective in distinguishing between fibrillation and A
8a ventricular tachycardia so that appropriate therapies may be delivered. Onset and rate stability criteria are discussed in the article "Onset and Stability for Ventricular Tachyar-rhythmia Detection in an Implantable Pacer-Cardioverter-Defibrillator" by Olson et al., published in Computers in Cardioloqy, October 7-10, 1986, IEEE Computer Society Press, pages 167-170.
It is envisioned that the onset and stability requirements are optional in a device employing the present invention, and preferably are made available as programmable options, which may be deleted by external programmer command.
If included, it is believed preferable that the onset criterion be required to meet prior to initiating counting of VTEC, and that once met, the criterion will remain satisfied wo g4/lC7C4 S3~fs PcT/uss3/l2222 .
until ~etecti~n of tacll~l~dia te~n~ t;on. Thus, onset is not inten~led to be a ~etection criterion required for re-detection of tachycardia, following initial detection.
The width criterion, if used, should also be understood to be useful both in initial cletection of tach~cardia and in re-detection of tacl-~. ~dia. This reflects a ~.c;.u~ ,Lion that following initial detection of ventricular tachycardia, absent a proven return to ~orm~l heart rhythm (telll~iualion detect), subsequent high ventricular rates should be l,.es~ d to be ventricular in origin. The stability criterion and the dis~ ;n~tor function may be ap~rol~liate for use both in initial detection and in re-detecti~n In ~tliti~n to the fibrill~tio~ and tachycardia ~letectio~ criteria ~liccllcced above in connecti~n with the Medtronic Model 7216 and Model 7217. The ~licrlQsedembo~lim~nt of the present invention also inrllldes additional detection criteria.
Initial detection of ta~:l~cardia or fibrill~tion detection may also be ~ccomplished using a comhin~l count of all intervals in~ tive of tacl~caldia or fibrill~tion. This comhine~ count (VFEC + VTEC) is rc.~ cd to a co.. ~ .e~l count threshold (CNID). If VTEC + VFEC is equal or ~atcr than CNID, the device checks to see whether VF~C is at least a predet~....inefl n..n.hcr (e.g. 8). If so, the device checks to determine how many of a number (e.g. 8) of the p;ece~ g intervals are greateror equal to FDI. If at least a predetermined number (e.g. 7) are greater than orequal to FDL tacll~ardia is initially detected, othel~ise ventricular fibrillation is initially ~lçtçcte~l The ~lCCG l;"g ~e~ cd intervals are then ~ e~l as ~lis~lcce~1 below to delelll~ e wh~lller the initial ~ ~oC;c of fibrill~fion or ta~h~r~ardia should be ~mçn~le~l to a ~ ~osic of fast ventricular tac~ dia.
The illustrated embo~lim~-nt of the present invention also ~efines two msll inteIval durations FIDI~ and FIDImjn. F~DIma,~ is an interval less than TDI and greater than FDI. FIDImin is an interval less than FDI. The device also ~efinec a third, overlapping interval range incltt(li~ intervals which are less than and ~ealer than or equal to FIDI~"in, which intervals are taken as indi~ ive of the po~cibility that a fast vent~icular ta l~car-lia is oc~ ;lIg, Both F~I~ and FIDImin are ~IO~ ~ hle values, and may either or both be set equal to FDI.
Following initial detection of tachycardia or fibrillation using, the most recent series of R-R intervals (e.g. the last 8 intervals) are examined to determine how many of the intervals fall within the fast ventricular tachycardia interval range. If at least a predetermined number of intervals (e.g. 7) fall within this range, the rhythm is diagnosed as fast ventricular tachycardia. The number of intervals required to diagnose fast ventricular tachycardia may vary depending on whether ventricular fibrillation or ventricular tachycardia is initially detected. For example the device may require that 7 of the preceding 8 intervals fall within the fast ventricular tachycardia interval range to diagnose fast ventricular tachycardia, if fibrillation is initially detected. Otherwise, ventricular fibrillation would be diagnosed. Conversely, the device may only require that at least 2 of the preceding 8 intervals fall within the fast ventricular tachycardia interval range in order to diagnose fast ventricular tachycardia, if tachycardia is initially detected. Otherwise, slow ventricular tachycardia would be diagnosed.
Other detection methods for recognizing tachycardias are described in U.S. Patent No. 4,726,380 issued to Vollman, U.S. Patent No. 4,880,005, issued to Pless et al, U.S. Patent No. 4,830,006, issued to Haluska et al., U.S. Patent No.
5,063,928, issued to Grevis et al. and U.S. Patent No.
4,969,465, issued to Pless et al., may also be used in conjunction with the present invention, as alternatives to the A 66742-5l0 ~ ~ ~ 3 2 4 ~ ~
detection method disclosed specifically herein. However, other detection criteria may also be measured and employed in conjunction with the present invention.
In the event that a tachyarrhythmia is detected, and an anti-tachyarrhythmia pacing regimen is desired, appropriate timing intervals for controlling generation of anti-tachycardia pacing therapies are loaded from microprocessor 524 into the pacer control circuitry 520, to control the operation of the escape interval counter and to define refractory periods during which detection of an R-wave by the R-wave detection circuitry is ineffective to restart the escape interval counter. Similarly, in the event that generation of a cardioversion or defibrillation pulse is required, microprocessor 102 employs the counters in pacer circuitry 520 to control timing of such cardioversion and defibrillation pulses, as well as timing of associated refractory periods during which sensed R-waves are ineffective to reset the timing circuitry.
In response to the detection of fibrillation or a 20 tachycardia requiring a cardioversion pulse, microprocessor 102 activates cardioversion/defibrillation control circuitry 554, which controls charging of the high voltage capacitor banks 560 via charging circuit 550, under control of high voltage charging lines 552, 553. The voltage on the high voltage capacitor banks may be monitored separately via VCAP
lines 538, 539 which are passed through multiplexer 532, and, in response to reaching the same or different predetermined A
7 ~ ~ 3 ~
values set by microprocessor 102, results in generation of logic signals on CAP FULL lines 542, 543, terminating charging of the capacitor banks. Alternatively, only one capacitor bank may be employed or two capacitor banks may be employed, charged together to the same voltage. Thereafter, the timing of the defibrillation or cardioversion pulse is controlled by pacer circuitry 520. One embodiment of an appropriate system for delivery and synchronization of cardioversion and defib-rillation pulses, and controlling the timing functions related to them is disclosed in more detail in U.S. Patent No.
5,118,105 by Keimel, cited above. However, any known cardioversion or defibrillation pulse generation circuitry is believed usable in conjunction with the present invention. For example, circuitry controlling the timing and generation of cardioversion and defibrillation pulses as disclosed in U.S.
Patent No. 4,384,585, issued to Zipes on May 24, 1983, in U.S.
Patent No. 4,949,719 issued to Pless et al., cited above, and in U.S. Patent No. 4,375,817, issued to Engle et al.
Similarly, known circuitry for controlling the timing and 20 generation of anti-tachycardia pacing pulses as described in U.S. Patent No. 4,577,633, issued to Berkovits et al. on March 25, 1986, U. S . Patent No. 4,880,005, issued to Pless et al. on November 14, 1989, U.S. Patent No. 7,726,380, issued to Vollmann et al. on February 23, 1988 and U.S. Patent No.
4,587,970, issued to Holley et al. on May 13, 1986.
In modern pacemaker/cardioverter/defibrillators, the particular anti-tachycardia and defibrillation therapies are ' - ~
12a programmed into the device ahead of time by the physician, and a menu of therapies is typically provided. For example, on initial detection of tachycardia, an anti-tachycardia pacing therapy may be selected. On re-detection of tachycardia, a more aggressive anti-tachycardia pacing therapy may be scheduled. If repeated attempts at anti-tachycardia pacing therapies fail, a higher level cardioversion pulse therapy may be selected thereafter. Prior art patents illustrating such pre-set therapy menus of anti-tachyarrhythmia therapies include the above-cited U.S. Patent No. 4,830,006, issued to Haluska, et al., U.S. Patent No. 4,727,380 issued to Vollmann et al. and U.S. Patent No. 4,587,970, issued to Holley et al.
The present invention is believed practicable in conjunction with any of the known anti-tachycardia pacing and cardio-version therapies, and it is believed most likely that the invention of the present application will be practiced in conjunction with a device in which the choice and order of delivered therapies is programmable by the physician, as in current implantable pacemaker/cardioverter/defibrillators.
In addition to varying the therapy delivered following a failed attempt to terminate a tachyarrhythmia, it is also known that adjustment of detection criteria may be appropriate. For example, adjustment may comprise reducing the number of intervals required to detect a tachyarrhythmia to allow a more rapid re-detection or by changing the interval ranges to bias detection towards detection of ventricular fibrillation, for example as disclosed in U.S. Patent No.
.~
~. ~.
-12b 4,971,058, issued to Pless et al.
The disclosed embodiment of the present invention also provides the ability to select from a menu of therapies for each type of detected tachyarrhythmia, as discussed above.
The therapy menu includes cardioversion and defib-rillation pulses of selectable amplitudes, as well as burst and ramp anti-tachycardia pacing modes for termination of ventricular tachycardias.
wo 94~16764 2~S
In bur~t pacing a series of ventricular pacing pulses is delivered at pulse intervals eqllal to a perceùtage of the average cycle length of the four R-R intervals prcce~ the point VTEC equals VTNID. If the burst sequence is ineffective in te,...;n~ the ta.l~ dia, a subsequent burst sequence may be delivered, at intervals of a lesser ~.,rce~ e of the average cycle length of the re-detected ta~l~c~dia The physician may pro~zuu the number of pulses per burst, the pcr~-~lage of tac~cardia cycle length, the number of sequences per burst pacing thcla~, the dcclclueuL in yclccnlage of cycle length with each s~lcce~ e burst and the ...;~ ... burst pulse interval. The burst pulses may be delivered in ~lem~n(3 mode or optionally in asyncl~onous mode. Ramp pacing delivers a number of pacingpulses, the first pulse interval being equal to a pcrcenlage of the average cycle length of the four R-R intervals prece~iing the point VTEC equals VTNID, with the interval l~cl._en pulses ~c~ c;..g with each pulse delivered. If the ramp sequence is inPff~ctive in te~ g the tacl~cardia, another ramp sequence may be delivered, with an initial interval of a lesser l.crce-~ e of the average cycle length of the re-detecte~l tacl~cardia and s~lbseq~lç-nt intervals collcslJo~ Iy reduced and with an m. l~,~cd ~ cr of pulses. The physician may yiO~ the n~n~bcr of pulses in the first ramp, the pcr~--~age of ta. l~caldia cycle length for the first interval, the cr of s~q~lenres per ramp pacing lLe~a~/~ the de~lcllle.l~ in ycrce-ol~e of cycle length with each s~lc~ ramp seqUçnre and the ~ --J~ pulse interval . The pulses may be delivered in dÇm~nd mode or optionally in a~llcllrollous mode.
Each ~1etçcte~ h~ia (slow VT, fast VT, fibrill~tion) may have, for cA~le, up to six s~ate thela~ies ~ro~ed for use seq~le.nti~lly, each delivered in rcsl,~,~c to the previously delivered therapy failing to telll i late the detectecl a,l~ia For ~ ~lc, slow VT might have two ramp pacing therapies ~rogl~.. c~l followed by two burst pacing Illela~ics. Fast VT might have ~nly one ramp pacing therapy, followed by one burst ~ela~, and then by cardioversion pulses of in~;lca~ m~ de FibAllation will typic~lly have four defibAllation pulse ~elapies of in~;leasing ~n~r~ de In the present invention, selection of the partic-ular electrode configuration for delivery of the cardioversion or defibrillation pulses is controlled via output circuit 548, under control of cardioversion/defibrillation control circuitry 554 via control bus 546. Output circuit 548 determines which of the high voltage electrodes 506, 508 and 510 will be employed in delivering the defibrillation or cardioversion pulse regimen, and may also be used to specify a multi-electrode, simultaneous pulse regimen or a multi-electrode sequential pulse regimen. Monophasic or biphasicpulses may be generated. One example of circuitry which may be used to perform this function is set forth in commonly assigned U.S. Patent No. 5,163,427, cited above. However, output control circuitry as disclosed in U.S. Patent No.
4,953,551, issued to Mehra et al. on September 4, 1990 or U.S.
Patent No. 4,800,883, issued to Winstrom on January 31, 1989 may also be used in the context of the present invention.
Alternatively single monophasic pulse regimens employing only a single electrode pair according to any of the above cited references which disclose implantable cardioverters or defibrillators may also be used.
The telemetry circuitry employed to practice the present invention in the device illustrated in Figure 1 includes telemetry timing/control circuitry 121, cyclic redundancy code circuitry 112 and uplink timing circuitry 118.
The operation of these circuit blocks and their inter-connection to the analog to digital converter 108, the A 667425l0 ~ ~ 5 ~
14a address/data bus 106, microprocessor 102, random access memory 104 and direct memory address circuitry 114 is discussed more fully in U.S. Patent No. 5,127,404, issued to Wyborny et al.
and incorporated herein by reference in its entirety. Also employed in the telemetry function are telemetry control circuitry 124, telemetry demodulator 122 and antenna driver 120, which are discussed in more detail below.
Figure 3, corresponding to Figure 4 of the Wyborny et al. patent illustrates the telemetry timing and control circuitry 121 in more detail. Telemetry timing/control circuitry 121 controls the formatting and timing of uplink telemetry, as described in the above cited Wyborny et al.
patent. Digital inputs to telemetry timing/control circuitry 121 are provided on multi-bit bus 106. Analog input to the telemetry A' 66742-510 W094/lC7C4 21$32~S ~IU593/12222 timing/control ~;uilly 121 is provided via analog to digital collve,ler 108, which co~ analog ~ign~1c, such as internal elcc1l0~s via ~mrlifier 534, the voltage of the output c~p~~itors as in~lic~teel on line 538, and other available analog inputs on line 110 such as battery voltage, etc. into digital format for tr~ ~C~ c~ion Both the S output ADC bus from analog to digital COll~Cl ler 108 and the address/data bus 106 are provided to a 12 bit data buffer 116 within telel,letl~ tirning\control ~ ;uih~ 121.
This buffer 116 is divided into two sectionc~ one section 119 sel~ing to store a four bit frame identifier code, the second section 117 SPlvillg to store a four bit upper nibble and a four bit lower nibble, which together make up a single data frame as described in above-cited Wyborny patent. Uplink timing block 118 decodes the 12 bits of data stored in data buffer 116 to produce a set of timing signals which key bursts of RF energy at the a~lol,liate times to pulse position mo~ te a 175 kilohertz carrier. Uplink timing 118 also keys bursts of RF energy at fL~ed position~
within the tC4~ frame col.e~ollding to the frame in;~ g pulse and the ~llcl~o~ ;.. g pulse, as illustrated in Figure 2, Aiccucce~l below. Cyclic re~hlnA~ncy code block 112 is employed to genelate the cyclic re~l----(l~--cy code used to provide fol. ard error ~etection in uplink telem~try~ and, may optionally also be employed for analyzing and ~ ; data received via downlink telemetry.
~el~ ~-;Qg to Figure 1, the output of timing block 118 is provided to telemetIy circuit 124 which, in re~c to receipt of signals from uplink timing block 118 ~ E,e~ the ~ e~ driver 120 to deliver bursts of RF energy to ~ntenn~ 125.
Telçmetfy ~mnA~ tion block 122 A~moAlll~tes pulse interval çn~o~le~l downlink tÇ~emetry reoe;~_d on ~ ç~ 124, and provides to telemetry block 124, which in turn provides the seAally l n~.c...;lle~l digital data rccei~cd via telemetry ~emo~ tor 122 into parallel format to delivery to microproceccor 102 via address/data bus 106.
Figure 2 illustrates the frame format of a telemetry IlA~ ;ccion accordillg to the present invention, and Ctilles~)ollr1s to Figure 2 of the above cited Wyborny et al.
patent. The basic unit of the format is a frame 30, having a duration of T"5. In the Aic~ l~sefl emboAimpntJ the main timing source for ge~l~lion of the telemetry frame ~ 30 col~ ises a st~n~1~rd 32.768 kiloherP crystal clock which provides a basic clock cycle WO 94/lC764 PCT/US93/1222, 21S3~5 . .
of 30.52 microsec~n~lc. Thus, a frame col~lised of 64 clock cydes eYt~Pn~ling over a fixed time interval of 1.953125 milliseconds provides a coll~el.ient frame, as the frame period is a binary multiple of the basic clock cycle. All signals within the frame coL.ll,lise bursts of RF energy, triggered by uplink timing ci~ iLly 118. The first signal is a frame signal 29 which de-finPs the l,c~;.,ni~g of the frame. The second signal is a ~llCll~Q ~ g signal CO~ g a burst 32 which is located at a time TG1 within fra ne 30. The frame identifier code is posifionPcl within the second fixed range of each frarne 30. The ;dentifier code colllplises an ~ Pntifier RF pulse 36 which is pulse position mod~llatetl to one of 16 available locations within the identifi=P-r range 38, and thus is a single bit heY~deçim~l value co~res~ol-ding to the 4 bit frame j~1Pntifier code stored in the first section 119 of data buffer 116 in telemetry timing and control clr~ y 121 (Fig.3). This single hexadecimal bit serves to identify the nature or type of data found within the frame.
Each frame also inrllldes two h~Y~decim~l bits coll-_s~Jo"r~ to the two 4 bit nibbles m~h~ Up the eight bit byte of data stored in the second portion 117 of data buffer 116 in tc~ r timing and control ~h. .~ 121 (Fig. 3). The telemetered data is enroded as two h~Y~ecim~l bits. The first heY~-lecim~l bit colles~ollding to the four least ci~ifi~nt bits of the byte is a pulse 42 positione~ within a third fixed range of frarne 3Q CO~ iug lower nibble range 44. The second hoY~de~m~l bit, c~ sp~ to the four most cierific~nt bits of the data byte is a pulse 46, p~Cisi~ne~ within a fourth fL~ced range of frame 3Q upper nibble range 48. Both the upper and lower nibble ranges inrlllde 16 identifi~ble pulse loc~fionc within the upper and lower nibble ranges 48 and 44, respectively.
The data ide-ntifier may fall within clock cycles 9-19 following the first clockcycle of the data frame, r3~ofinPd by the delivery of the frame pulse 29. As indicted in the below, de~e~ g on which cycle the frame pulse falls, a variety of types of data may be in~lir~te-l Data ~ Pntifier codes in~ de a ~ lber of mP~c~lred analog values inrl~ in~ the present level of VDD (5 Hex), battery voltage me~ l cn'ent (6 Hex) and the di~elel-ce (delta V.) between 1~P~ ;ng and trailing edges of battery voltages (7 Hex), analog EGM (8 Hex), and the voltages on two output capacitor 5 ~
banks (9 and A Hex). In addition, telemetry of programmed parameters (0 Hex) may be identified. Of most importance with regard to the present invention, however, are the marker (2 Hex) and marker supplement (3 Hex) data types.
The present invention, like the Medtronic Model 7216 and 7217 implantable pacemaker/cardioverter/defibrillators includes an extensive set of marker codes to be transmitted in conjunction with sensing of intrinsic depolarizations, and in conjunction with delivery of bradycardia pacing pulses, anti-tachycardia pacing pulses, as well as cardioversion and defib-rillation pulses. These marker codes are listed in the table illustrated in Figure 4a. Figure 4a also includes reserved marker codes for use in conjunction with future devices which may also employ electrodes adapted to sense atrial heart rhythms and also includes marker designations for delivery of atrial anti-tachycardia and defibrillation therapies. On receipt by an external programmer, these marker codes are translated into graphical signals for display in conjunction with a sensed electrocardiogram, as described in U.S. Patent No. 4,374,382, issued to Markowitz et al., describing the basic functioning of marker channel transmissions as presently used in many commercially available pacemakers. Graphic symbols corresponding to the marker codes are illustrated for ventricular events in Fig. 4g. Atrial events could employ the same symbols but with reversed polarity (i.e. extending below the baseline).
,~4 2 ~ 5 3 ~ ~ ~
17a In addition to markers simply designating the type of individual events which occur, the present invention usefully provides marker supplement data, which is uplinked following the marker codes when the pacing interval of the device is greater than or equal to 100 milliseconds. Each block of marker supplement data is transmitted in the form of five sequential frames, each containing one byte of marker supplement information. Available information is formatted into the five marker supplement bytes, as indicted in the tables 4b, 4c, 4d, 4e and 4f, with information listed in order of priority for inclusion as part of a marker supplement transmlsslon.
Figure 4b illustrates the binary codes for the data bits in marker supplement frame one. These 8 bit binary bytes are encoded as two hexadecimal bits for ~ ~, WO 94tl6764 ~ PCTtUS93tl222 ', 21S32~'3 ;on, as ~ se~ above. Supplement data byte one is a general device status byte, broken into four two and one bit subunits. The first two bits are related to the status of the device vis a vis its telemetry operation, the third bit indic~tes whether a tachy~lLylhl,lia episode is in process, the fourth bit indicates whether any previous tacl~ ,ia episodes had been detected since the last time the memory was cleared, and the sixth and seventh bits indicate the ~ nçes under which the VT event connter was most rccel,lly reset.
Figure 4c illustrates marker supplement byte two, in a format co-,e;.~onding to Figure 4b. Byte two, ~ ed in the second marker supplement frame, either provides i~U~ n with regard to the status of the VF event counter or the status of the high voltage output c~p~ritor charging process and the status as to whether one of a llulllber of available therapies is being delivered. Status with regard to the VF event countçr is ~ ed as an alterative to il to.~ation indjc~ting the particular type of lhe~ , esenll~ being delivered, and/or in-lic~ting high voltage c~r~citor cL~g, as the VF event counter is disabled during cha~g and during delivery of anti-tacl~ lhll,ia thelap.cs. As intli~te-l in ~igure 4c, status in~ tors with regard to slow VT, fast VT and VF ~hel~ies are available, with theability to deci~te which of six physician selected therapies for each of these three ta.:l~ll~lh~;a tiia~oses are being delivered. This il.iollllation, in conjunction with i~ru~ t;on with regard to the therapies chosen by the physician, allows for a more con~plete lm~lP-~st~n~ling of the f~lnrtioning of the device.
Figure 4d illu~llates marker supplçm~-nt byte three, in a format colle~ollding to Figure 4b. The third marker supplement byte either in'~ t~PS the status of the VT
event count or the VT therapy scan ll-~ber presently in ylu~e;~s. These data types are ~llc ~t;~res to one another, in that the VT detection operation is disabled during delivery of an anti-tacl~ ~ia therapy. As ~lic~lcsed above in conjunction with the burst and ramp anti-tachycardia pacing therapies, each therapy may be repe~t~l for a llu.-lber of se~lP-nres or scans, before going on to the next therapy. In the event that such a lllela~ is being delivered, the third mark supplement byte will in-lic~te which scan or sequence of the selected therapy is presently being delivered, WO 94/16764 ~ S3~s PCT/US93112222 further enh~nring the physician's underst~n~ling of the therapy being delivered.Conversely, if the device is not delivering a therapy, the VT event count would ~cco...r ~ny a VF event count in marker supplement byte two, providing a more complete underst~nding of the ~roE;less towards tach~llJ~rthmia detectior S Figure 4e illustrates marker supplement byte four, in a format col~e~ollding to Figure 4b. Marker supplement byte four provides a telemetered value of the ~P~ ed R-R interval prece-ling the pacing pulse or sensed ventricular depolqri7~ti~ n, and can be used in conjunrtion with the increm~nted values of the VT and VF event counts, to further refine the physician's underst~n~ling of the detection methodQlogy Figure 4f illustrates marker supplement byte five, in a format collesponding to Figure 4b. Marker supplem~o-nt byte five is a status byte, when the first bit is zero, the re-..A;-~;-.g bits are used to in~ te status of detection and therapy pro~;1----"i"g The second bit ;-~ ec whether VF therapies are IJlo~;~ cd on. the third bit being used to in~ic~te whether fast VT therapies are pl~Og~ ~-"",rd on and the fourth bit being used to in~lir~ted whether slow VT Illela~:es are ~,u~; ~ ..ed on. The fifth bit is employed to in~li~te whether VF ~letectiQn is activated, the sixth, seventh and eighth bits being used to indie~te whether fast VT detection via VF is pro~; ~ ned on, and whether VT detection is l,lo~ .. ed on. With the first bit at 1, the 1~-.-~;.. ;.. ~ bits inrlulle h~rolll~ nn as to ~Leth~r the .. P~ rCd elc~tlu~ll width met the width criterion and, and as to the ...P~ .ed electrogram width.
As devices accordhlg to the present invention lJio~es5, it is ~nti~ip~ted that ~d~lition~l types of marker status h~folmalion will be added, particularly in cQnjnnrtion with devices which sense and treat atrial a~ h...;~c, and as additional detection methodologies and criteria are added. For example, in conjunction witha device as (licclose~ in the present application, additional marker supplement bytes which in~lic~te whether the onset criteria has been satisfied, whether the rate stability criterion has been ~ticfied or whether other tachycardia detection criteria such as the width ~P~ enl and V-T/V-F dis~ or filnctionc described above have been s~ticfied are certainly well within the scope of the present invention. Similarly, marker status bytes indicating the status of detection of atrial arrhythmias and the status of delivery of therapies for treating atrial arrhythmias will be included in devices which have these capabilities.
While the prefe,led embodiment of the device takes the form of a microprocecsor controlled device as illustrated in Figure 1, in which the operation of tbe device is controlled by stored software, the invention may equally well be pr~cticed in the form of a ~lefli~tell~ full c~lctom digital integrated circuit or, even in the form of an analog circuit, employing analog values as substit~ltes for the digital values ~liccl~sed in conj!~n~ n with the above specification.
In ~dditiQn~ while the preferred embo~liment ~iic~lQsed above takes the form of a p~cem~-Pr/cardioverter/ defibrillator, the enh~nce~ ability to telemeter i~ol...~l;on regardillg detection of tachyarrhythmias and delivery of anti-arrhythmia tberapies provided by the present invention are also valuable and applicable to devices which are only capable of pelrolll.il,g a subset of the various therapies ~iccllcce-l above in cQ~ ;Qn with Figure 1.
It should further be kept in mind tbat while the tberapies described for delivery in respQ~e to ~letection of the various ~rlh~rL~iaS ~licc~lcsed are all~liccl~!se~ in the ~u..t~ ~l of electric~l therapies, it is possible that the invention may be embodied in the form of an impl~nt~ble drug dispellser, wherein one or more of the anti-~acl~dia ~el~pies takes the form of injection of a drug locally into the heart or ~le~ ly to treat the detected arrhythmia. As such, the above ~licclos~re should be taken merely as an eY~mple of an embo~limpnt of the present invention,rather than l;..-;L;i~g, when reading the claims which follow.
In co-j,~ ;Qn with the above specific~tion~ I claim:
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An implantable device, comprising:
means for detecting heart depolarizations;
means for measuring a parameter associated with said detected depolarizations;
means for detecting an arrhythmia, said detecting means comprising means for defining criteria for detection of said arrhythmia as a function of said measured parameter, over a series of said detected depolarizations, including means for storing an indication of the relative progress toward said meeting said criteria and for updating said stored information following detected ones of said depolarization; and means for telemetering information following individual ones of said detected depolarizations to an external receiver, said information comprising said updated stored information as to the relative progress toward meeting said criteria.
means for detecting heart depolarizations;
means for measuring a parameter associated with said detected depolarizations;
means for detecting an arrhythmia, said detecting means comprising means for defining criteria for detection of said arrhythmia as a function of said measured parameter, over a series of said detected depolarizations, including means for storing an indication of the relative progress toward said meeting said criteria and for updating said stored information following detected ones of said depolarization; and means for telemetering information following individual ones of said detected depolarizations to an external receiver, said information comprising said updated stored information as to the relative progress toward meeting said criteria.
2. An implantable device according to claim 1, wherein said means for detecting an arrhythmia comprises means for detecting at least first and second arrhythmias, said detecting means comprising means for defining criteria for detection of said first and second arrhythmias as a function of said measured parameter, over a series of said detected depolarizations, including means for storing an indication of the relative progress toward said meeting said criteria for detection of said first and second arrhythmias and for updating said stored information following each detected depolarization and wherein said telemetering means comprises means for telemetering information following individual ones of said detected depolarizations to an external receiver, said information comprising said updated stored information as to the relative progress toward meeting said criteria for detection of said first and second arrhythmias.
3. An implantable device according to claim 1 or claim 2, further comprising:
means for defining a plurality of stimulation therapies to treat a said detected arrhythmia, said stimulation therapies comprising multiple stimulation pulses;
means for selecting a said therapy;
pulse generator means for delivering said selected therapy in response to detection of a said arrhythmia; and means for telemetering an indication as to which of said therapies is being delivered, following individual ones of said stimulation pulses.
means for defining a plurality of stimulation therapies to treat a said detected arrhythmia, said stimulation therapies comprising multiple stimulation pulses;
means for selecting a said therapy;
pulse generator means for delivering said selected therapy in response to detection of a said arrhythmia; and means for telemetering an indication as to which of said therapies is being delivered, following individual ones of said stimulation pulses.
4. A device according to claim 1, 2 or 3 wherein said measuring means comprises means for measuring the interval separating a said detected depolarization from a preceding detected depolarization.
5. A device according to claim 4 wherein said means for defining said criteria comprises means for defining an interval range and for defining said criteria in the form of a required count of said measured intervals which fall into said interval range and wherein said means for storing an indication of the relative progress toward said meeting said criteria and for updating said stored information following each detected depolarization comprises means for storing and updating a count of said measured intervals falling within said interval range with each said detected depolarization.
6. An implantable device according to claim 3 wherein said means for defining said therapies further comprises means for defining therapies each comprising a plurality of sequences of said stimulating pulses and wherein said telemetering means further comprises means for telemetering an indication of which of said plurality of sequences is being delivered, following delivery of individual ones of said stimulating pulses.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002256997A CA2256997C (en) | 1993-01-29 | 1993-12-15 | Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/010,970 US5383909A (en) | 1993-01-29 | 1993-01-29 | Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation |
| US08/010,970 | 1993-01-29 | ||
| PCT/US1993/012222 WO1994016764A1 (en) | 1993-01-29 | 1993-12-15 | Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002256997A Division CA2256997C (en) | 1993-01-29 | 1993-12-15 | Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2153245A1 CA2153245A1 (en) | 1994-08-04 |
| CA2153245C true CA2153245C (en) | 1999-04-27 |
Family
ID=21748288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002153245A Expired - Fee Related CA2153245C (en) | 1993-01-29 | 1993-12-15 | Diagnostic telemetry system for an apparatus for detection and treatment of tachycardia and fibrillation |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5383909A (en) |
| EP (2) | EP0681495B1 (en) |
| AU (1) | AU673410B2 (en) |
| CA (1) | CA2153245C (en) |
| DE (2) | DE69328881T2 (en) |
| WO (1) | WO1994016764A1 (en) |
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- 1993-01-29 US US08/010,970 patent/US5383909A/en not_active Expired - Lifetime
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- 1993-12-15 EP EP97123019A patent/EP0850661B1/en not_active Expired - Lifetime
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| WO1994016764A1 (en) | 1994-08-04 |
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| DE69328881T2 (en) | 2000-11-09 |
| AU5850094A (en) | 1994-08-15 |
| EP0681495A1 (en) | 1995-11-15 |
| DE69319928T2 (en) | 1999-04-15 |
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