CA1105564A - Continuous electrocardiogram monitoring method and system for cardiac patients - Google Patents

Abstract

Abstract of the Disclosure A system which is capable of allowing an attending physician to continuously monitor the electrocardiogram (ECG) signals produced by a cardiac patient. The signals, generated by the patient, are first recorded in real time over a predetermined time period established by the physician.
At the conclusion of the predetermined time period a monitoring station is automatically alerted by telephone and commences receiving the patient's real time ECG signals directly. The recorded ECG signals are then transmitted in a compressed time fashion to the monitoring station simultaneously with the real time ECG signals. The monitoring station receives the compressed time and the real time transmitted signals and following analysis thereof transmits a report of selected portions of the ECG to the physician. Upon instructions from the physician, the monitoring station either returns the recording apparatus to its normal operational status for a predetermined time period, or continues to receive and analyze the real time ECG signal until the patient's signal is sufficiently stable and then returns the recording apparatus to its normal operational status. This process repeats continuously. The physician communicates directly with the monitoring station and with the patient as may be required.
The system and method provides close and complete monitoring of the patient with complete ECG, data retrieval and individual-ized close patient surveillance.

Description

Background of the Invention 6 It has been recognized by physicians that it is 7 extremely important to continuously monitor cardiac patients 8 imm~diately following coronary attacks. Such is normally 9 accomplished very effectively in the coronary care unit of most American hospitals where the patients are continuously 11 monitored following heart attacks to detect arrhythmias of 12 the heart, particularly warning ventricular arrhythmias which 13 may lead to ventricular fibrillation and death. Through ~~ ~
14 prompt recognition and treatment of these warning ventricular arrhythmias in coronary care units, the mortality rate of 16 acute myocardial infarctions has been reduced by one half.
17 In addition, approximately 15% of post myocardial infarction 18 cardiac patients continue to have frequent ventricular extra 19 systoles (more than 20 per hour) after discharge from the hospital and while in an out-patient status.

22 ~his experience has led physicians to the 23 recognition that it is desirable to continue such direct 24 intensive monitoring of the high risk cardiac patient's ECG signals subsequent to release from the cardiac care unit.
26 Constant monitoring of these patients after release from the 28 hospital is difficult because of the logistics involved and `` il(~55~4 I particularly since they can no longer be monitored closely

2 I as a group by direct wiring or close telemetry such as is

3 possible in a hospital. As a result, various systems have

4 I been developed to attempt to monitor the ECG signals of

5 ¦ out-patients to thereby provide a diagnostic tool for

6 ¦ additional treatment or variation of treatment for the patients

7 ~ as may be required.

8 l

9 The systems currently in existence for such out-patient ECG signal monitoring basically fall into four 11 main types, which are, portable tape recorders, telephone 12 transmission devices, radio transmission devices, and tape 13 recorders which use telephone transmission. While èach of 14 these devices operates quite well, there are in each of the systems disadvantages and limitations which preclude safe, 16 close and continuous monitoring of the ECG signals generated 17 ¦ by the out-patient. Since the warning ventricular arrhythmias 18 which lead to ventricular fibrillation may develop at any 19 time and without prior indication and, in fact, sometimes without the patient even recognizing such is occurring, 21 that is, no physical symptoms are immediately present, it is 22 apparent that the patient may expire during the time when the 23 cardiac signals are being recorded but are not to be soon 24 reviewed.

26 The typical portable tape recorder systems currently 27 in existence must be worn continuously by the patient for 28 ___ ll~SS64 -~
1 the period of time for which they are designed to record;
2¦~ typically 12 to 26 hours. The device weighs from one to 3 ~ two pounds and thus is relatively heavy and uncomfortable to 4 the patient. Subsequent to the time during which recording 5 I occurs, the recorder is returned to the medical facility by 6 the patient where the tape can be removed and the device can 7 be placed in condition for a new recording. The recorded 8 tape is then analyzed and a report thereon is transmitted to the 9 attending physician who can then decide further activity or treatment as may be required. Obviously, such devices 11 result in a delayed data retrieval and analysis in that the 12 tapes are returned only subsequent to the predetermined 13 recording period (between 12 and 26 hours). In addition, 14 there is a further delay while the patient returns the tape recorder to the scanning facility, the scanning facility 16 analyzes the recording, compiles a report and transmits it 17 ¦ to the physician. Thus, during the time when recording 18 ceases and until the tape is removed, no recordation of the 19 ECG signal is being made. As can also be seen, these devices have a severe distance limitation in that the recording must 21 be scanned at a specialized medical facility and thus is 22 impractical for patients who live long distances from such 23 facility.

As further evidence of the limitations of these 26 devices reference is made to the January, 1977 issue of 27 Circulation, An Official Journal of the American Heart S6~
1 Association, Inc., Volume 55, No 1, page 210 and 211; and to 2 the May 26, 1977 issue of The American Journal of Cardiology 3 Volume 39, pages 873-879; and to the May 1972 issue of Archives 4 of Internal Medicine, Volume 129, pages 773-779. These three 5 I articles report deaths occurring from ventricular fibrillation 6 while the patient was wearing a tape recorder.

8 Some of the telephone transmission devices are 9 designed in such a way that they will automatically detect a warning arrhythmia and sound an alarm to thereby alert 11 the patient. The patient is then expected to telephone the 12 medical facility to transmit the ECG signals which have 13 been converted to a frequency modulated signal within the 14 I audio ran~e of the telephone. Some of the devices do not 15 ~ have an automatic arrhythmia detection system but instead 16 ! depend upon the patient recognizing a symptom such as 17 palpitations, chest pain, shortness of breath or lightheaded-18 ¦ ness which may be caused by the warning arrhythmia. If the 19 patient recognizes the symptom, the patient then dials 22o the medical facility and transmits the signal by telePhone.

22 These telephone transmitting devices have a number o~ short-comings. It is obvious that the warning arrhythmias causing 23 the symptoms or the automatic alert to occur are missed 24 because the medical facility can only begin to record once 225 the patient has completed the call. Thus the medical ~ facility only begins to record subsequent to the occurrence 27 ¦ of such warning arrhythmias. It is obviously also impractical 28 I for the patient to maintain the telephone contact with the Il 5 I

`' llC5564 lj medical facility ~or longer than a few minutes time during 2~l which the patient must remain by the telephone. Thus only a 3 ~ very small amount of ECG signal data is, in fact, ever 4 ~ received or recorded by the medical facility. As above 5 , noted often a patient will not recognize the symptoms of a 6 ¦ warning arrhythmia and thus this warning arrhythmia may never 7 ¦ be recorded. In addition the patient may be incapacitated 8 ~ by the arrhythmia or already unconscious and thus is unable 9 to complete a telephone call and may expire prior to any data being transmitted to the medical facility. Furthermore, 11 if the patient's ECG signals are to be transmitted for any 12 substantial period of time the telephone lines at the 13 patient's home and the medical facility may be tied up for 14 substantial periods which adds to inconveniences as well as 15 ¦ tremendous expense.

17 The radio transmission devices again operate upon 18 the principle of detecting arrhythmias through the use of 19 electronic logic networks. When such occurs the radio transmission capability is actuated and the ECG signals are 21 transmitted through the use of a UHF or VHF radio transmission 22 to a central medical facility capable of recording and 23 analyzing the signals. Obviously, these devices suffer from 24 distance limitations in that the radio transmissions are typically line of sight and may also have tremendous 26 reliability problems in that the UEIF and V~IF siqnals may be 27 disturbed as a result of concrete-steel construction which 28 ~ may exist b ween the patlent and the central receiving SS64 ~, 1 I facilltv . There are also only a limited number of radio 2¦¦ channels allotted to this type of transmission which 3 I automatically limits the number of patients capable of being 4 ~ monitored within the receiving range of any medical facility.
5 ~ Furthermore, the problem with respect to incomplete data 6 retrieval as above-described is also inherent in a system 7 of this type. In addition, the radio transmission devices 8 as well as the telephone transmission devices which have the 9 automatic detection systems therein, suffer from the additional problem in that the signals which cause the activities of 11 the system are typically warning arrhythmias. These devices 12 allow no way to quantitate total heartbeats or to detect 13 trends which reflect the rate or QRS morphology changes.
14 These latter provide information supplemental to the detection of arrhythmias which information is significant to a physician 16 treating a high-risk cardiac out-patient. Furthermore, 17 ¦ there is no way to tell what warning arrhythmias are not 18 being detected by the electronic logic in the radio trans-19 mission devices and, in fact, significant arrhythmias may be missed which cannot be verified because only limited 21 portions of the ECG signal are being retrieved.

23 Where the portable tape recorder is utilized along 24 with the telephone transmitter system, one can immediately ascertain that the incomplete data retrieval above referred 26 to exists in addition to the tyinq up of telephone lines 27 both at the patient's home and at the medical facility. In ~8~

I

"~ 5564 ---1~l addition thereto, one skilled in the art will recognize that 2¦1 by continuously recording, rewinding and replaying the 3 I recorded information on the tape less than one-half of the 4 patient's ECG signal history is being recorded and transmitted.
5 I If the patient is required to frequently record and play back, 6 ¦ for example, in ten minute intervals, it will immediately 7 ~ also be seen that the patient is constantly calling the medical 8 facility every 20 minutes to transmit his 10 minute recorded 9 signal. Such would mean that he would be telephoning the medical facility approximately 72 times through a 24 hour 11 period which, obviously, becomes impractical for a high-risk 12 cardiac out-patient.

14 The best prior art known to applicant is described in the following United States Patents:
16 3,199,508 3,880,144 17 3,212,496 3,882,277 18 3,267,934 3,893,453 19 3,434,151 3,972,320 3,603,881 3,910,260 21 3,650,263 3,934,267 22 3,724,455 3,946,744 23 3,742,938 3,951,135 24 3,768,017 3,~58,563 3,779,237 3,86,498 26 3,832,994 3,~91,747 27 3,639,907 3,913,567 28 ___ ~:- llC5S64 ~

1 ~u~mary o~ the Invention 2 I A system for continuously monitoring ECG signals 3 I from a patient comprising means for recording atrial and 4 I ventricular ECG signals in real time at a predetermined rate 5 ~ along with means for reproducing the prerecorded signals at a 6 I different rate which is greater than the rate at which the 7 signals were recorded so as to compress the time required to 8 reproduce the signals as compared to the time required to 9 originally record the signals. Means for monitoring the reproduced signals is connected through a communications 11 interface with the means for reproducing the signals thereby 12 to enable a qualified person to analyze the signals and provide 13 appropriate care for the patient.

A method for continuously monitoring ECG signals 16 from a patient including recording atrial and ventricular ECG
17 ¦ signals in real time at a predetermined rate and reproducing 18 I the prerecorded signals at a different and greater rate so 19 as to compress the time required to reproduce the signals as compared to the time required to originally record the 21 signals, monitoring and analyzing the reproduced signals 22 and providing treatment for the patient responsive to the 23 information on the reproduced signals.

Brief Description of the Drawings 26 Figure 1 is a block diagram generally i]lustrating 27 the continuous monitoring system for cardiac patients 28 ___ ~ 115564 ~'`J' 1 I constructed in accordance with the present invention;
2 l 3 I Figure 2 is a block diagram showing in more detailed 4 form the patient station of the system;
5 ~
G Figure 3 is a block diagram showing in more detailed 7 form the monitor station;
9 Figure 4 is a block diagram showing the patient station of the system in yet further detail;

12 Figures 5, 6 and 7 are flow charts illustrative of 13 the various operational steps within the system;

Figure 8 is a generalized block diagram showing 16 the control logic utilized in the system of the present 17 invention;

19 Figure 9 is a tim;'ng diagram illustrative of the time during which various signals may occur throughout 21 the functioning of the system constructed in accordance with 22 the present invention; and 24 Figure 10 is a graph illustrating a typical electrocardiogram signal wave form recorded by the monitoring 26 station portion of the system constructed in accordance with 271 the present invention.
28 ___ ~0 1` ;.,; 11~564 .~ .

1ll Detailed Description 2 As is illustrated in Figure 1, to which reference 3 is hereby made, a system constructed in accordance with the 4 present invention, includes a patient transmitter 10 which may be worn at all times by a patient who is under cardiac 6 care. The patient transmitter includes a state of the art 7 telemetry transmitter apparatus which may transmit ECG
8 signals as indicated by the communication link 12 to a patient 9 station which is in the form of a portable console or similar apparatus. Obviously, other ~hysiological signals 11 such as blood pressure, pulse rate, respiratory rate and 12 the like may also be transmitted if desired and would be 13 useful to the attending physician. For ease of illustratlon 14 and clarity of description, only ECG signals will be referred to throughout but it is intended to include other physiological 16 signals as well. It should also be understood that the 17 patient's station may be powered by pluyging into the standard 18 wall electric outlet or alternatively may be battery powered.
19 Thus the patient's station may be carried by the patient such as between work and home or the like and maintain 21 continuous recording of the ECG siqnals. The patient station 22 14 includes means to record, in real time, the ECG signals 23 developed by a patient. In addition thereto, the patient 24 station also includes means for reproducing or playing back the prerecorded ECG signals in a substantially compressed 26 time as compared to the real time re~uired to record the 27 signa A telephone interface 16 is connected between the ],1 I
, S64 `~

1I patient station 14 and a monitoring stati.on 18. Through the 2 11 utilization of appropriate control means the telephone 3 instrument is activated to provide both the compressed time 4 reproduced signals (as illustrated by the solid lines between the blocks) as well as the real time signals (as illustrated 6 ¦ by the dashed lines between the blocks) directly to the 7 monitoring station 18. As a result, the patient's ECG signals 8 both real time and prerecorded are being monitored at the 9 monitoring station 18.

11 After analysis of the ECG signal being received 12 selected portions thereof are transmitted to the physician 13 for his review. An additional telephone interface 20 is ---14 provided to permit direct communication between the monitoring station and the physician 22. In the event such may be 16 required, the physician can communicate not only with the 17 monitoring station but also with the patient as is illustrated 18 by the arrows at each end of the lines between the blocks 19 14-22. Through these lines either the physician or the monitoring station, upon orders of the physician, may 21 communicate to the patient or to the patient station any 22 desired and detailed informati.on, depending upon the outcome 23 of the analysis of the ECG signals recei~ed from the patient 224 both as a result of the reproduced and real time signals being 26 received.
27 ___ 28 ___ ~ 12 ll(~S56~ `-11 It will be recognized by those skilled in the art 2 ¦ that a system constructed in accordance with the present 3 I invention which provides a continuous monitoring of ECG
4 I signals may be utilized in various ways. Obviously, one of these ways is to monitor cardiac out-patients during the 6 approximately six month period subsequent to release from a 7 hospital during which they are most susceptible to ventricular 8 fibrillation and other lethalarrhythmias and as a result 9 thereof, expiration. In addition thereto, such patients normally are under medication or exercise programs or a 11 combination of both, and in many instances have undergone 12 aorto-coronary saphenous vein bypass graft surgery. Little 13 ¦ is known at the present time regarding the exact effects of 14 exercise, medicines and surgery upon ventricular arrhythmias.
Long range investigation, study and analysis is required 16 to provide the data which will result in better utilization 17 of drugs, exercise and surgery in treating cardiac patients.
18 An apparatus constructed as is the system of the present 19 invention will definitely provide this immediate capability since it is extremely simple, lightweight, easy to use and 21 requires little or no direct involvement of the patient 22 other than the wearing of the electrodes and the liqhtweight 23 telemetry transmitter.

In addition, a continuous monitoring apparatus 26 constructed in accordance with the present invention may 27 also be utilized in intensive care coronary units in modern ~ J
11I hospitals for the purpose of permitting the patient's ECG
2 signals to be applied to a computer properly programmed to 3 analyze the same for quantitation of arrhythmias and the 4 like. At the present time only a very small percentage of coronary care units throughout the country utilize computers 6 becatlse of the large expense involved for the purchase of computers. The system of the present invention alleviates 8 this prcblem because the patient's ECG signals may be trans-9 mitted directly to a central computer serving multiple hospitals with a summary report being trans~itted to the 11 coronary care unit from this central computer. The several 12 patients in each coronary care unit would have their pre-13 recorded time compressed and real time ECG signals 14 transmitted serially over a single telephone line. The monitoring technician would coordinate and cycle these 16 transmissions. Thus one computer managed by one monitoring 17 technician can follow multiple patients from multiple 18 coronary care units with minor expense for each of the 19 coronary care units involved. Similarly, rest and convalescent homes where many of the elderly patients are subject to 21 coronary disease and arrhythmias may utillze this system with 22 minimal equipment to the great benefit of the patients involved.

24 As above pointed out, when a patient is on an exercise program of some type such as utilization of a 26 stationary bicycle or jogging in place for set periods of 287 time and/or at set workloads, the apparatus of the present .
I
j 14 ~1 "
1 ~ i~vention may be worn thus providing ECG signals to the 2 monitoring station. From analysis of these ECG signals it 3 can be detected if arrhythmias increase, decrease, or remain 4 the same as a result of such exercise programs and thus whether medication or treatment should be undertaken or 6 modified. Similarly, some cardiac patients have arrhythmias 7 but at very infrequent times. It is extremely important 8 with respect to such patients that they be continuously 9 monitored to detect these infrequent arrhythmias. By the continuous monitoring of the present system, such infrequent 11 arrhythmias occurring even, for example, such as once per 12 week or twice per month may be detected simply because the 13 patient's ECG signals are being continuously monitored and 14 the technician and/or computer will detect such arrhythmias when they are transmitted. In addition, the continuous 16 monitoring capability of the system of the present invention 17 ¦ may also be useful in detecting rare malfunctions 18 occurring in a permanent pacemaker worn by a patient. The ~9 only way to detect and repair such malfunctions is to monitor the patient until the malfunction occurs and is reflected in 21 the ECG.

23 Referring now more particularly to Figure 2, the 24 patient station 14 is shown in somewhat more detail. As is therein illustrated, a telemetry receiver 24 receives the 26 signal transmitted from the telemetry transmitter 10. The 27 signal received by the telemetry receiver is applied to a 28 ___ ilUSS64 '' F.M. modulator 26 which frequency modulates the received 2 I signals about a 1000 hertz center frequency. The signals 3 are also applied simultaneously to a rate-rhythm alarm 28 4 which will be discussed more in detail below. The output si~nals from the modulator 26 are applied to a tape recorder 6 32. The tape recorder has a record mode wherein the signals 7 applied thereto are recorded in real time at a first pre-8 determined rate of recording such, for example, as 15/16 9 inches of tape per second. When the predetermined time period during which recording occurs expires and communication 11 with the monitor station has been established, an appropriate 12 control circuit will stop the recording, rewind the tape 13 rapidly, and then cause the tape to play back at a very 14 rapid speed as compared to the original recording speed, for example, at 18.75 inches of tape per second (20 times 16 faster than the recording speed). Thus the time required 17 for reproducing the signals recorded upon the tape is 18 compressed substantially as compared to the original time of 19 recording of said signals. When the compressed time playback has been completed and the end of the tape or a signal from 21 the monitor station is received indicating that the time 22 required for the playback has expired, whichever occurs first, 23 the tape is then again caused to rewind at a rapid speed and 24 the system is returned to a record mode to record the signal received from the patient in real time. As will be obvious 26 to those skilled in the art it is not necessary that the tape 27 be rewound at each point in order to accomplish the reproduction 28 __ 1l of the signals prerecorded thereon at the compressed time.
2 ¦ For example, a continuous tape may be provided in cassette or 3 ~ reel to reel form with appropriate cue marks appearing thereon.
4 ~ When the appropriate cue marks arrive at the record head, 5 I appropriate control circuits can be energized which will place 6 the tape recorder and associated equipment 32 into the play-7 back at compressed time mode thus causing the signals to be 8 immediately transmitted at the compressed time unit until an 9 additional cue mark is received at which point in time the tape transport is again returned to a record in real time mode.
11 Obviously, the tape may be played back at an increased speed 12 in a reverse direction if desired.
13 ~ -14 The signals received by the receiver 24 are also applied to a F.M. modulator 30 which is connected directly to 16 the telephone interface 46, During the time the tape recorder 17 is not recording the patient's ECG signals they are being 18 transmitted directly over the telephone in real time to the 19 monitor station.

21 During the time that the prerecorded signals are 22 played back in compressed time, the signals thus reproduced 23 are applied to a demodulator 34 which operates at the approxi-24 mate multiple of the recording center frequency (e.g., 20 times) such as at a 20,000 hertz center frequency. Such 26 is required since the original signal from the telemetry 27 receiver is F.M. modulated at a 1000 hertz center frequency 28 __ 11~5564 ~ ~
1~ and has now been increased to 20,000 hertz by the 20 times 2 I record speed playback. An additional modulator 36 is coupled 3 ¦ to the demodulator 34 to modulate the resulting signal at 4 ¦ 3000 hertz center frequency which is within the passband 5 , required for transmission over the telephone line. This 6 I signal is then applied through the patient's station telephone 7 ¦ interface 46 for transmission over the telephone line 40 8j to the monitoring station 18.

11 As is noted, the phone dialer 50 has connected 12 thereto a timer 52. The timer controls the point at which 13 the system dials the monitoring station. The timer 52 may be 14 set or reset by the monitor technician throu~h the control 16 logic to any desired time period at the direction of the I physician to control the periodicity of the contact with the 17 ¦ monitor station and thence the rewinding and playback of the 19~ signals being recorded by the tape recorder 32.
22o 22 As indicated, the signal from the telemetry 23 receiver is also applied to the rate-rhythm alarm 28. In the event that the patient's real time received ECG signals deviate from a predetermined pattern, thus indicating the 26 occurrence of a severe bradycardia, or severe tachycardia, or 27 a dangerous arrhythmia (e.g. more than five ventricular ectopic beats (VEB) per minute), the rate-rhythm alarm will 2~3 1! 18 1 I detect such and through the control logic 51 will automatically 2 i activate the phone dialer 50 which, through the utilization 3 of the distance direct dialing techniques currently available, 4 through the patient station's telephone interface 46, immediately alerts the monitoring station 18 which will commence 6 to receive the real time ECG signal over the telephone line 7 40.

9 l ! From a consideration of the block diagram as shown 11 in Figure 2, it will be recognized by those skilled in the 12 art that the patient generating the ECG signals is constantly 13 being monitored by the recording equipment 32 and/or~the 14 monitoring station 18. Through the utilization of the timer 52, the patient's real time signals being recorded can be replayed 16 at any interval desired by the physician from a few minutes 17 to hours as the case may be depending upon the history of the 18 patient at that particular point in time. This occurs 19 without the patient being aware of any changes that may have taken place. The only requirement of the patient is that 21 he maintain himself in a position such that the telemetry 22 transmitter 10 and the telemetry receiver 24 remain in 23 radio contact at all times. Typically such transmitters 24 have a very effective range of approximately 500 feet depending upon the particular local conditions, thereby 26 providing ample movement by the patient in his normal day 27 to day activities, either at home or at work. A call button 28 204 may be used by the patient to activate the telephone 11 as ~lCS~
1I will be explained more fully below. A tone detector or 2¦¦ monitor 214 is used for control purposes as will also be more 3 fully explained below.
4 I Referring now more particularly to Yigure 3, the 5 ¦ monitor station 18 is shown in further detail. As is therein 6 shown the signals on the telephone line are passed through 7 a line select switch 49 and to the monitor station telephone 8 interface 53. The com2ressed time signal is applied by way 9 I of a connection 62 to a high pass filter 64 and from there to a demodulator 66 at 3,000 hertz center frequency to thus 11 develop a first signal which is representative of the compressed 12 time signal, in accordance with the present example at 20 13 times the recorded real time signal. This reproduced - - ~
14 compressed time signal may be applied to any device desired to assist the technician at the monitor station in analysis 16 of the signal. For example, this signal may be applied to 17¦l1a computer, an oscilloscope, a strip chart recorder, a tape 18 Irecorder or a combination of all of these.
19 , The signal from the patient's station which is 21 transmitted in real time is coupled over the line 80 to 22 a low pass filter 82 and to a demodulator 84 at 2000 hertz 23 which in turn produces a real time signal. The real time 24 signal likewise may be applied to the computer, oscilloscope, strip chart recorder, tape recorder or 26 any combination thereof as again may be required to assist 27 the technician in his task. The monitor technician receives 28 ~¦the in ormation from the various recording and/or readout ~ 20 1 devices and analyzes the same. The monitoring technician 2 may generate a desired tone signal as indicated by the 3 Itone-l switch 54, tone-2 switch 56 and tone-3 switch 58.
4 Such switches activate appropriate logic as illustrated at 55, 57 and 59, respectively. Timer switches 70 are used 6 by the monitor technician to set or reset the timer 52 7 at the patient's station. Upon setting the switch 70, 8 appropriate control signals are generated at 72 and are applied 9 to the data transmission logic 59 and over the telephone line

10 Ithrough the control logic 51 to the timer 52. Likewise the

11 tone signals are applied through the monitor station telephone

12 interface 53 to the patient's station for purposes as will be

13 described more fully hereinafter.

14 l The output signals from the demodulator 66 are also 16 applied to a rate-rhythm (RTOR) interval detection device 68 which 17 ¦ produces an output signal indicative of any changes in the pulse 18 rate or rhythm thereof of the patient. The signal is also applied 19 to a digital data detection means 74 which along with the conversion and display logic means 76 and display 78 provides 21 patient identification and specific information regarding the 22 patients such as total heartbeats; total VEB's, timer setting 24 and the like.
The monitor technician may also provide a summary 2276 report with particular rate-rhythm samples to the physician 2 by way of the telephone interface 20 (Figure 1) and by way of 8 utilization of communication methods that may be available .

1l, to him such, for example, as a telephone copying apparatus, 2 ¦I The physician reviews the transmitted information and if 3 I required, contacts the patient directly by voice communication.
4 ~ If desired, the physician may direct that there by a change in the 5 ¦ setting of the timer 52 to a different recordin~ period as may 6 be indicated from the samples provided by the monitoring 7 technician. As will also be recognized to those skilled in 8 the art, the monitor technician may directly contact the 9 physician (if he is not present) and alert the physician as to any difficulties which immediately appear to the monitor 11 technician so that the physician may immediately contact the 12 patient for consultation or instruction and obtain also the 13 real time ECG signals for purposes of direct analysis thereof;

By now referring to Figure 4, a more detailed block 16 diagram of the patient's station 14 is illustrated. As is 17 ; therein shown the control logic module 200 is interconnected 18 I with various additional portions of the patient's station.
19 ¦ Functions of the control logic module will be discussed in 20 ¦ more detail hereinafter, It will, however, be noted that 21 ¦ the tape recorder 32 is connected through the cable 202 to the 22¦ Control logic module in such a manner that the control logic 231 module can provide signals to stop, record, play and rewind 241 the tape and additionally, the tape deck can provide a signal 251 to the control logic module indicating that the end of the 26¦ tape has been reached (EOT).

281 __ ass64 ~ ~
~¦l A call button 204 is interconnected also to the 2 ¦¦ control logic module 200 and is utlized by the patient 3j should such be required to automatically dial the monitoring 4 station 18 simply by depressing the call button 204. Such may be required in the event the patient is experiencing 6 I symptoms which require immediate attention by the monitor 7 I technician or by the physician. An appropriate call light 206 8 is also interconnected with the control logic module and provides 9 the patient with a means to determine whether the system is using the telephone line.

12 In the event the doctor or the monitoring station 13 wish to alert the patient and to have him communicate by -- -14 voice over the telephone there is provided an audible alarm and light 208 which is connected with the control logic module.
16 Thus, in the event the doctor or monitor technician activates 17 the system appropriately (Tone-2) a sound will occur that 18 ~ should alert the patient to immediately lift up his telephone 19 ¦ and talk with the doctor and additionally a light will flash on and off to visually indicate that such should be done.
21 Additionally, a patient alert transmitter 209 is provided 22 to signal the patient by radio transmission in the event 23 he is remote from the patient station.

A busy check and disconnect apparatus 210 and 212 26 are interconnected between the telephone apparatus 11 and 27 the control logic module 200 for purposes to be described ..

S564 ~
11 more ftllly hereinafter. Basically, this permits the system 2 to determine whether the telephone is being used for other 3 purposes, for example, the patient is talking to someone 4 and, if so, after an appropriate wait, and a warning signal, 5 to disconnect the same, in order to dial the monitor station, 7 Tone detectors or monitors 214 are also interconnected 8 with the system and receive appropriate indications confirming 9 occurrences within the system as will be more fully described 10 below.

12 Also provided is an appropriate switch and isolation 13 means 216 which is interconnected between thë controi logic 14 module and the telephone line to accomplish the appropriate

15 switching of the signals as generated onto the telephone

16 lines and to operate the phone system appropriately.

17

18 F.M. modulator 30 is connected to receive the real

19 time signals from the receiver 24. The F M. modulator 30

20 has a center frequency of 2000 hertz. This real time signal

21 and in addition thereto, the compressed time signals which

22 have been modulated by the F.M. modulator 36, are coupled

23 through the amplifier 217, the line 220, and the switch

24 and isolation means 216 to the telephone line. An appropriate 2~ busy signal may be applied from the control logic module by 26 way of the connection 222 as an input to the amplifier 217 27 __ 2~ __ 1 lC S~
11 also thus providing an indication that the telephone will be 2 busy. Appropriate switches 224 and 226 are incorporated between 3 the signals and the control logic module 200 to provide 4 appropriate activation such as selection of the signals or insertion of digital data for recording and/or transmission as 6 will be more fully described below.

8 Referring now to Figures 5, 6 and 7, there is 9 presented a flow chart indicating the various functional operations which occur within the patient's station at 11 appropriate times. These times have been broken into various 12 increments and identified as PO through P13 each of which 13 will be discussed individually below. `

When the system is plugged in to an appropriate 16 electrical outlet and into the four prong telephone jack or 17 other telephone standard connectors normally provided, the 18 power switch is first turned on which permits the entire 19 system to clear and the logic to reset. Certain portions of the logic are set causing the system to dial the monitoring 21 station for initial contact or to re-establish contact 22 after an inadvertent power loss. At this point in time, 23 the rate-rhythm alarm is activated and may commence operation 24 at any time in the event of receipt of abnormal arrhyth~ias as above-described.
26 __ 27 __ 28 __ ass64 ~-, 1 The first step is at PO. During P0 the telephone 2 ¦ is available to the patient, the tape recorder is oPerating 3 I and is recording the real time signal upon the tape, there 4 ¦ has been no rate-rhythm alarm signal indicating an abnormal arrhythmia requiring immediate attention and the patient's 6 telemetry transmitter is working properly. During this period 7 of time any one of four things may occur. A tone 1 or tone 3 8 may be received. In the event one of these tones occurs, 9 it indicates that either the doctor has called the patient and wishes him to respond or alternatively, the patient has 11 called the doctor (through or at the monitor station) and 12 wishes to communicate as a result of some problem. The 13 doctor or monitor technician by activating the appropriate~ ~ ~
14 tone, can, in fact, cause the equipment to connect to the telephone line without any assistance from the patient.
16 ~rhe second thing which may occur is that the call button may 17 ~ be activated as a result of the patient or his agent having 18 pushed the same. Such will cause a call to the monitor 19 station and/or doctor. Automatically the same thing ~ould occur in the event of a rate-rhythm alarm or a power-on-clear 21 signal having occurred indicating that the power was off and 22 came on again. In addition to the above two items, there 23 may also occur an end of tape signal. If such occurs it 24 means that the tape has run out and if that does occur, the tape is stopped thus avoiding any damage to the tape transport 26 equipment. Such also activates the dialing and causes the 27 monitor station to be called.
28 __ SS6~

1¦l The fourth thing that may happen during PO is 2¦l that the timer runs to within one minute of the time previously 3 set thus indicating that it is time to call.

If any of the four items above referred to occurs, 6 then the light 206 is energized indicating that the system 7 is in condition such that the telephone should not be used 8 and the system goes to program step Pl or P4 depending upon 9 which event occurred.

11 Program step P1 is the one minute warning time 12 indicating that there is only one minute of recording 13 time left until the timer causes the unit to call thè - ~
14 monitor station. The busy check 210 system determines whether or not the telephone is being u~ed and is thus busy.
16 If the telephone is busy, a busy signal is provided to alert 17 ¦the telephone user that it is time that the telephone be cleared 18 ¦because the monitor station will be called within one minute.
19 ¦If the phone is busy then the system continues to provide 20 ¦the busy (beeper) sound and check to determine if the phone 21¦ remains busy.

231 If, in fact, the phone continues to be utilized 24 ¦throughout the entire one minute period of time and is 251 still busy at the expiration thereof, then at P2 the control 26¦ logic module 200 through the dial switch (disconnect) 212 227~ automatically disconnects and overrides the party using the 5S6~ ~J

1I telephone to permit dialing of the monitor station. This 2 I automatically occurs at the end of the time set by the 3 ~ timer 52.

Once the automatic dialing has occurred, the system 6 checks to see if there is a connection to the monitor station 7 at P3. If the monitor station is not connected to the phone 8 line within the time limit (2 minutes) then the system goes 9 automatically to P2 which again causes the system to dial the monitor station.

12 During program step P3 the real time ECG signals 13 are connected by way of the telephone line to the monitor 14 station. During this time a check is made by the patient's station for confirmation that it is, in fact, connected to the 16 monitor station. If a confirmation signal from the monitor 17¦ station has not been received, then a two minute time out 18 sequence is established. If no confirmation signal is received 19 during this two minute period then the system is reset to step P2 and the monitor station is again dialed. The 21 confirmation by the monitor station, that it is, in fact 22 on the line is transmission of a tone 1 or tone 3 timing 23 signal to the system. Additionally, tone 1 may also be 24 utilized for other purposes at different points in the program, such, for example, as breaking the connection at 26 the end of a particular playback period thus stopping the 27 __ 28 __ 5564 `--`
playback of the prerecorded signal and allowing the telephone 2 I transmission to terminate.
3 l 4 Thus once the confirmation of the connection of the monitor station to the patient station has been received, 6 whether during step PO or P3, the unit then progresses to 7 step P4. In step P4 the tone 1 received signal is cleared, 8 In the event the patient has depressed the call button, such 9 call button request is cleared. Thereafter, an identification lO ¦ code is applied from the control logic module 200 through the 11 switch 224 into the amplifier 30 and it is recorded and 12 also through switch 226 it is transmitted to the monitor 13 to thereby identify the patient's station which is about to ~
14 transmit the compressed signal. This code signal can also contain other digitally coded data, for example, the setting 16 of the timer 52 and the total number of heartbeats since the 17 last playback from the total counter 29.

19 At this stage the system progresses to P5 wherein the tape transport is caused to stop the movement of the 21 recording tape. Thereafter, at P6, the tape is caused to 22 rewind until the beginning of thetape (BOT) is received, 23 at which point the system at P7 stops the rewinding of the 24 tape. At P8 the playback of the prerecorded ECG signals in a compressed time mode is accomplished. This playback 26 continues until the end of the tape is reached or a tone 1 28 __ ~ li~5S64 `~
li or tone 3 signal is received at the patient's station. If 2 I any one of these three events occur the playback of the 3 ¦ tape is stopped at ~9. When the playback of the tape is 4 stopped, the system progresses to P10 where the tape is rewound, to Pll where the rewinding of the tape is stopped, 6 and subsequently to P12 where the system returns to the recording 7 of the signals from the patient's telemetry transmitter in 8 real time. Such continues again until the end of the tape 9 has occurred or the timed period of recording has occurred if no tone 1 signal has been received from the monitor station.
11 In the event such occurs, the system immediately returns to 12 step P4 to again replay the information appearing on the 13 tape. In the event a tone 1 is received at the conclusion 14 of P12, such indicates that the monitor station has received the recorded signal and is completed with it and wishes 16 the system to continue in its normal mode of recording and 17 release the phone line until the next call occurs. If such 18 occurs the system then goes to P13 which clears the tone 1, 19 releases the recorder and causes the telephone to hang up when and if not in use by the patient talking with the 21 monitor station. The system then returns to P0.

23 Tone 2 has its own specific program since it is 24 a non-synchronous type of activity and such is illustrated in Figure 7 to which reference is hereby made. In the event the 227 physician wishes to talk to the patient during a time when 28 __ ~ , `SS64 ;~

1~ the system is in use, the monitor transmits a tone 2 signal 21~ to the patient's station. If a tone 2 signal occurs, such will 31i first cause the system, through the control logic module, 4 ¦ to clear tone 2 and to then determine whether or not the phone is husy by going through a phone busy check at 210.
6 In the event the phone is busy, contact is established 7 already so the ECG signals are immediately connected to the 8 phone system so the physician may receive them. In the 9 event the phone is not busy, then the audible and visual alarm 208 is activated, thus causing the patient to 11 recognize that he should immediately pick up the phone to 12 talk with the doctor or monitor technician. Under these 13 circumstances, the doctor may be placed in direct co~munication ~
14 with the patient.

16 As indicated in Figure 8, to which reference is 17 ~ hereby made, the control logic module is a standard state-of-18 the-art system wherein a clock provides a continuous clock 19 signal to the logic module. There is provided a program counter which is a standard 4 bit binary counter which then 21 applies a signal to a decoder which is a standard 4 bit 22 binary to 16 line decoder. The output of the decoder is 23 applied to the function control system which includes standard 241 gates and flipflops well known to those skilled in the art.
The various functions above referred to are interconnected 26 to the control logic module as is indicated by the various 27 __ 28~

5564 `"

1 portions of the system and are identified by the same reference 2 I numerals. It is thus not believed that additional detailed 3 ~ description or discussion with respect to Figure 8 is 4 required.

6 From the foregoing it will now be recognized by 7 those skilled in the art that during the normal sequence of 8 operations of the continuous monitoring system constructed 9 in accordance with the present invention, assuming that the recorder has been recording the patient's ECG signal in real 11 time, the following events will occur. When the timer reaches 12 the one minute warning time indicating that there is only 13 one minute of recording time left, a busy signal is placed _ 14 upon the phone line, if in fact the phone line is in use, thus providing a warning to the user that he should hang up 16 the phone. At the same time, the call light becomes activated 17 indicating that the telephone line is in use and should 18 not be picked up. The timer then will go through the remaining 19 one minute of recording time and reaches that position when the monitor station should be called. The unit automatically 21 dials the monitor station and at the same point in time places 22 the ECG signal on the line. The patient's station then waits 23 for a period of up to two minutes for a confirmation signal 24 from the monitor station, either tone 1 or tone 3 indicating that the monitor station has received the call and is ready 26 itself to r eive the compressed time pla~back electrocardiogram 28 __ ~.', li(~SS6~

l~l sianals. The tone signals are carefully chosen so that 2I they do not interfere with nor will they be responsive to 3 ¦ the normal signals occurring in telephone use, for example, 4 ~ dial tone, ring tone, busy tone, or tones used for dialing.
5 ¦ If the patient station does not receive the confirmation signal 6 within this two minute period of time it then hangs up 7 the telephone and automatically dials again. ~hen the 8 confirmation signal (tone 1 or tone 3) is received from the 9 monitor station, then the identification code and other digitally coded data of the patient station is recorded 11 on the tape and transmitted to the monitor station on the 12 compressed time signal frequency (3000 Hz) where it is decoded 13 and displayed. The recorder at this point in time s`tops, - - ~
14 rewinds and plays back the recorded data at the compressed time as, for example, 20 times faster than the original 16 recording time. The playback at this compressed time 17 ¦ continues until the end of the tape is reached, unless 18 during the playback a tone 1 or tone 3 signal is first 19 received. Such a signal would normally be issued wnen the identifying code recorded in P4 is observed indicating the 21 end of the latest recording has been reached.

23 Subsequent to the playback occurring, the recorder 24 stops, rewinds and again starts recording the real time signal from the patient's telemetry transmitter. In the event a tone 1 26 or a tone 3 signal was received, it is echoed on the carrier 27 of the 3000 hertz modulator along with the other digital data.
28 __ r . 1 i~55~

1 I Such a tone 3 signal is a timing data signal which establishes 2 the time for recording of the real time data thus causing the 3 I system to cycle at any desired point in time. Such can be 41 done by the physician or the technician at the monitor station, upon orders of the physician, in the event either more frequent 6 monitorin~ or less frequent monitoring is required of this 7 particular patient, without termination of the 8 connection. In the event a tone 1 signal has been received, 9 during or subsequent to the playback, the tape is rewound, recording commences, and then the patient's unit releases 11 the phone line. If the patient is talking on the phone 12 or the clear leader of the tape is still passing the 13 record head, the real time data will continuë to be transmitted ~
14 over the phone line until such a time as the patient hangs up the phone and the tape is being recorded upon, thus 16 permitting the appropriate operation to occur to thereby 17 release the telephone line.

19 As above noted, the signal at the monitoring station may be utilized in various fashions. One of the 21 utilizations is to apply the signal to a computer which has~
22 been properly programmed to analyze ECG signals. The computer 23 accepts the time compressed data received from the patient's 24 station, detects and quantitates total heartbeats and arrhythmias. The computer is programmed to quantitate the 26 total num~er of supraventricular extrasy-stoles and the 27 number of ventricular extrasystoles. It further clarifies 28 __ ass64 1ll the ventricul~r e~trasystoles into single, paired, multiform 2 11 and ventricular tachycardias. These classifications, as well 3 I as any others desired by the physician, of the significant 4 I warning arrhythmias and other data, allow comparison of the 5 ¦ patient's progress on the periodic basis, for example, assuming 6 ~ that the patient's tape recorder is established for a one hour 7 ~ recording period then the patient's progress is compared on 8 ¦ an hour by hour basis.

The technician attending the monitoring station 11 should be a highly trained person, usually a coronary care 12 nurse. This technician scans the information usually by 13 reference to the oscilloscope or to the strip chart-recorder - ~ ~
14 which is providing a visual permanent record of the material which is being transmitted. At the same time, the technician 16 would scan the computer readout. By analyzing the strip 17 chart recording and the computer readout the technician would 18 determine the need for continuing real time transmission of 19 ECG signals currently being received at the monitoring station.
If the need exists, the technician allows this transmission 21 to continue by failing to transmit a tone 1 signal back to the 22 patient station. If, however, the technician does not 23 determine the requirement for a continuation of real time 24 transmission of the ECG signals, then the monitor technician will provide a tone 1 signal to the patient's station thus 26 causing the transmision to cease and the tape recorder 27 to again commence recording the real time signals as above 28 ~~

` 11~5564 ~

1 I set forth.
2 ~ .
3¦ Subsequent to receipt of the signal and the scanning 4 I thereof, the technician selects representative samples of any 5 ¦ significant arrhythmia or electrocardiogram abnormality from 61 the strip chart recording and combines these with the 7 ¦ computer record, thus providing a periodic summary report of 81 this particular patient. The summary report is sent by a 9¦ telephone copying device to the physician who may be anywhere 10¦ that is equipped with a telephone, e.g., his office, the 11¦ hospital or his home. Obviously, the physician may be at 12¦ the same site as the monitoring station, e.g., the coronary 13¦ care unit and would directly receive the information. Upon - -~
14¦ receipt of the periodic report on his telephone copying 15¦ apparatus, the physician is now in a position to scan the 16¦ summary and determine what may be required insofar as additional 17 ¦ treatment for this particular patient. It can thus be seen 18 I that a continuous and rapid monitoring of a patient occurs 19 ¦ wherein ECG history is quickly analyzed and treatment varied as 20¦ required. By way of example, utilizing a system as of the 21¦ type above set forth, approximately three minutes is required 22¦ for the telephone tran~mission fror the patient to the monitorin~
231 station, assuming that a one hour tape has been rewound and played 241 back. Four additional minutes is required for the computer to 251 print out and the monitor technician to select arrhythmia samples.
26¦ Typical telephone copying requires six minutes; thus the 271 final summary report for the hour reaches the physician in 28 ~

S~

ll 14 minutes following the transmission of the ECG information 2I from the patient's station. If the tape recording is 3 ~ occurring on an hour by hour basis, the physician receives 4 I hourly reports of all heartbeats of the patient within 73 5 ~ minutes at most from the time which they occur.

7 If the patient is being monitored on a 10 minute 8 recording basis, then the heartbeats of the patient will get 9 to the physician within 20 minutes of occurrence. It requires 10 minutes to record in real time, approximately 30 11 seconds for telephone transmission, 1 minute to analyze and 12 recognize arrhythmias and 2 minutes to assemble the summary 13 report. Thereafter the report is telephone copied in the re~uired 14 6 minutes.

16 When the system continues in real time, that is, 17 the real time signals are connected to the monitorin~ station, 18 then reports are issued to the physician immediately where 19 indicated. As also above noted, a tape recorder is in existence at the monitoring station and will receive all 21 of the signals being transmitted whether compressed or real 22 time and thus preserves a permanent record of those signals 23 for future review should such be necessary.

By way of further examples to illustrate use of the 26 present system, a typical patient treatment will now be 27 given. If a patient has a large number of arrhythmias 28 occurring, for example, more than 20 ectopic beats per hour 1 llass64 ~

1~ then he will be continuously monitored in real time until the 2l' ectopic beats are controlled to the satisfaction of the 3 ~ physician. Also when a patient is first released to out-4 ~ patient status, he will be monitored on a real time basis 5 ¦ until the ectopic beats are in a condition satisfactory to 6 ¦ the physician. Thereafter, the patient's ECG is recorded 7 for short time periods (for example 10 minutes) and is then 8 played back. If there are no arrhythmias detected during several 9 playbacks, then the recording time is progressively extended, for example to 20 minutes, then 40 minutes, and then 60 minutes.
11 Thereafter the patient's ECG is followed for 60 minute intervals.

13 In the event the scan discloses arrhythmiàs have~
14 occurred, then the monitor technician changes the review period to such shorter time as the physician prescribes 16 Of course, after each monitor period a summary report is 17 provided the physician with particular emphasis on any arrhythmias 18 noted.

Reference is now made to Figure 9 which provides 21 a timing diagram that correlates the various inputs, outputs 22 and logic functions with the particular step P0 through P13 23 in the program for the patient's station. The various 24 portions of the bar graph utilize the code wherein if the area following the input-output or flip-flop is cross hatched, it 2~ means the particular signal indicated may occur during that 27 particular point in time. If it is completely clear it 28 _ G5564 ~ ~`

1 means that it cannot occur during that particular time.
2 1l If it is solid, it means that the particular input-output 3 I or flip-flop is activated during that particular point in 4 time. Thus, for example, the calling light is on throughout ~ function steps Pl through P12 while, on the other hand, the 6 ¦ one minute warning input is on only during function step Pl, 7 that is, the one minute warning function step, As an 8 additional example to assist in reading the timing chart 9 the stop signal which causes the tape to stop will occur always in function steps P5, P7, P9 and Pll and may occur 11 during steps PO through P4 depending upon whether an end 12 of tape (EOT) signal is received. As would be anticipated 13 from the foregoing discussion, the rate-rhyth~ alarm is on -14 at all times when the patient's unit is not connected to the monitor station PO and thus may be activated as a result 16 of abnormal bradycardia or tachycardia. It is believed 17 that with the foregoing explanation and by reference to the 18 flow charts, Figures 5, 6 and 7, that the timing diagram 19 will be self-evident and thus additional discussion thereof is not required herein.

22 Reference is now made to Figure 10 which represents 23 a typical strip chart recording made utilizing a system 24 constructed in accordance with the principles of the present invention. As is therein shown the graph at 250 represents 26 the real time patient's ECG signal being received and recorded 27 ¦ at the monitor station. Such, of course, would occur during 28 I __ 1l all periods of time that the monitor station is connected, 21l including times when the tape recorder is not recording the 31~ signal being received. As will be recalled from the foregoing 4 I discussion, when the end of the tape occurs with the system 5 ~ connected or the confirmation signal is first received from 6 the monitoring station, an identification code is first 7 transmitted and such is as illustrated at 260 in Figure 10.
8 The tape recorder ceases recording the patient's heartbeat at 9 the commencement of the identification code, however, the monitor station is now recording the ECG signal while the identification 11 code is transmitting in real time to the monitoring station 12 and simultaneously therewith is recorded on the tape at the 13 patient's station at the end of the patient's signal recording 14 time. Subsequent to receipt and recordation of the patient's identification signal or code, the tape transport commences the 16 rewind of the tape and such is illustrated at 262 on Figure 10.
17 At the conclusion of the rewind time the tape recorder commences 18 to play back the prerecorded signal at a compressed time, and 19 in accordance with the preferred embodiment, at 20 times the previously recorded rate. Such compressed playback signal is 21 shown at 264 in Figure 10. It will be noted that throughou~
22 this entire period of time the signal 250 has continued to 23 be recorded. At the conclusion of the 20 times recorded 24 signal playback, the identification code 260 is again played back but at this point in time at 20 times its previously 26 recorded rate. Such playback of the identification code 27 indicates the termination of the recording of the most 28 recently recorded signal.

5564 ~-1¦l As is illustrated in Figure 10, during the time 2 ~ compressed playback of the ECG recording the patient may 3 I experience an arrhythmia which will be immediately detected, 4 .For example premature ventricular extrasystoles occur at 266 and 268 on the real time tracing 250, Alternatively, these 6 arrhythmias may have occurred during the prerecorded ECG and 7 would be detected both in the rate-rhythm curve 270 as shown 8 ¦ at 271, 273 and 275 and by scanning the compressed ECG 264 9 where the ventricular extrasystoles are depicted at 274, 276, and 278, Upon such detection that part of the ECG would be expanded 11 and provided to the physician as part of the summary report.

13 From the foreoging it can be seen that a complete 14 record of a cardiac patient's ECG signals is maintained and transmitted to a central monitoring station where a 16 permanent record is maintained and the electrocardiogram 17 material is properly analyzed. Such analysis enables a 18 trained person to ascertain whether arrhythmias are occurring 19 and if so, whether they are such as to lead to ventricular fibrillation. In addition thereto, appropriate quantification 21 of axrhythmias occurs and this has prognostic value. In 22 the event 20 or more ventricular extrasystoles per hour occur, 23 such is a definite warning sign and in cardiac patients 24 is associated with a higher probablity of sudden death. The rhythm, of course, must be monitored for the full 24 hours to 26 objectively quantitate all the arrhythmias that occur during 27 the day and night. In addition to identification thereto by 28 __ 15S-~4 11 having the electrocardiogram signal available for monitoring, 2¦1 the configuration of the electrocardiogram complex itself 3 ¦ may be obtained. That is, the ~RS and ST segments of the 4 ~ electrocardiogram signal may reflect the degree of ischemia, 5 ~ that is, blood supplied to the heart. Thus, elevation or 6 ¦ depression of the ST segment of the electrocardiogram may 7 ~ suggest certain diagnosis as the etiology. This deviation of 8 ¦ the ST segment can occur without associated arrhythmias and, ¦ o 1tself, be of great importance.

Z~

2~

Claims (25)

WHAT IS CLAIMED IS:

1. Continuous monitoring system for cardiac patients comprising:
means for recording electrocardiogram signals produced by the patient in real time at a first predetermined rate;
means for reproducing said recorded signals at a second predetermined rate, said second predetermined rate being greater than said first predetermined rate thereby compressing the time required to reproduce said signals as compared to the time to record said signals;
means for monitoring said reproduced signals; and a communication interface coupling said reproducing means to said monitoring means.

2. A system as defined in claim 1 wherein said means for recording includes a transmitter means for attachment to the patient and receiver means tuned to receive signals transmitted by said transmitter means which signals are representative of electrocardiogram signals from said patient.

3. A system as defined in claim 2 wherein said means for recording further includes modulator means for frequency modulating a carrier having a first frequency responsive to variations in said received signals repre-sentative of said electrocardiogram signals.

4. A system as defined in claim 3 wherein said means for recording further includes a magnetic tape recording medium upon which said frequency modulated signals are recorded as said tape moves at a first predetermined speed and are reproduced as said tape moves at a second predetermined speed, said second speed being faster than said first speed.

5. A system as defined in claim 4 wherein said reproducing means includes a demodulator means having a carrier having a second frequency, said second frequency being greater than said first frequency by an amount proportional to the difference between said first and second speeds.

6. A system as defined in claim 1 which further includes timer means for controlling the periodicity of transmission of recorded electrocardiogram signals from said recording means to said monitoring means.

7. A system as defined in claim 6 wherein said timer means includes means for changing the timer at said recording means and at said monitoring means.

8. A system as defined in claim 1 which further includes means for detecting a variation in the repetition rate of said electrocardiogram signals beyond predetermined limits and automatically establishing a communication with said monitoring means responsive thereto.

9. A system as defined in claim 1 which further includes means for detecting a variation in the rhythm of said electrocardiogram signals beyond pre-determined limits and automatically establishing a communication with said monitoring means responsive thereto.

10. A system as defined in claim 1 which further includes means for detecting a variation in the repetition rate and the rhythm of said electrocardiogram signals beyond predetermined limits and automatically establishing a communication with said monitoring means responsive thereto.

11. A system as defined in claim 1 wherein said communication interface includes a telephone system having direct distance dialing capability.

12. A system as defined in claim 11 which further includes an automatic telephone dialing means coupled to said telephone and timer means, said timer means activating said automatic dialing means for controlling the periodicity of transmission of recorded signals from said recording means to said monitoring means.

13. A system as defined in claim 12 which further includes means for detecting a variation in the repetition rate of said electrocardiogram signals beyond predeter-mined limits and providing an output signal responsive thereto, and means for connecting said output signal to said automatic dialing means for establishing communication with said monitoring means.

14. A system as defined in claim 12 which further includes means for detecting a variation in the rhythm of said electrocardiogram signals beyond predeter-mined limits and providing an output signal responsive thereto, and means for connecting said output signal to said automatic dialing means for establishing communication with said monitoring means.

15. A system as defined in claim 12 which further includes means for detecting a variation in the repetition rate and the rhythm of said electrocardiogram signals beyond predetermined limits and providing an output signal responsive thereto, and means for connecting said output signal to said automatic dialing means for establishing communication with said monitoring means.

16. A system as defined in claim 1 which further includes means for simultaneously transmitting said electro-cardiogram signals in real time to said monitoring means with said reproduced signals.

17. A system as defined in claim 16 which further includes, at said monitoring means, means for making a record of said reproduced and real time electrocardiogram signals.

18. A system as defined in claim 17 wherein said means for making a record is a strip chart recorder.

19. A system as defined in claim 17 which further includes means for communication with a physician including a communication interface with said monitoring means and a communication interface with said patient.

20. A system as defined in claim 19 which further includes means for alerting said patient to communicate verbally with said monitoring means or said physician.

21. A system as defined in claim 1 which further includes indicator means for providing an indication to said patient that said system is producing said signals and providing said signals to said means for monitoring.

22. A system as defined in claim 1 which further includes indicator means for providing an identification of said patient to said monitoring means.

23. A system as defined in claim 1 which further includes means for totalizing said patient's heartbeats and transmitting said total to said monitoring means.

24. A method of continuously monitoring electro-cardiographic signals of cardiac patients comprising:
recording the electrocardiogram signals produced by the patient in real time at a first predetermined rate;

reproducing said recorded signals at a second predetermined rate, said second predetermined rate being greater than said first predetermined rate thereby compressing the time required to reproduce said signals as compared to the time to record said signals;
transmitting said reproduced signals by telephone to a station remote from said patient; and analyzing said reproduced signals.

25. A method as defined in claim 24 which further comprises the step of simultaneously transmitting-the real time electrocardiogram signals along with said reproduced signals on said telephone to said remote station.