WO2002028478A1 - Implantable medical device with pressure measurement means - Google Patents

Implantable medical device with pressure measurement means Download PDF

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Publication number
WO2002028478A1
WO2002028478A1 PCT/SE2001/002150 SE0102150W WO0228478A1 WO 2002028478 A1 WO2002028478 A1 WO 2002028478A1 SE 0102150 W SE0102150 W SE 0102150W WO 0228478 A1 WO0228478 A1 WO 0228478A1
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WO
WIPO (PCT)
Prior art keywords
pressure
signal
intravascular
medical device
pressure signal
Prior art date
Application number
PCT/SE2001/002150
Other languages
French (fr)
Inventor
Kjell Norén
Charlotte Kjellman
Kenth Nilsson
Sven-Erik Hedberg
Original Assignee
St. Jude Medical Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by St. Jude Medical Ab filed Critical St. Jude Medical Ab
Publication of WO2002028478A1 publication Critical patent/WO2002028478A1/en

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Classifications

    • 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
    • A61N1/362—Heart stimulators
    • A61N1/365—Heart stimulators controlled by a physiological parameter, e.g. heart potential
    • A61N1/36514—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure
    • A61N1/36564—Heart stimulators controlled by a physiological parameter, e.g. heart potential controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by blood pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body
    • A61B5/02156—Calibration means

Definitions

  • the invention relates to an implantable medical device according to the preambles of the independent claims.
  • An absolute pressure sensor is disclosed in US-5,535,752.
  • the disclosed sensor is a capacitive type of sensor.
  • An implantable lead having a sensor module formed in its distal end is coupled to a monitor that powers a sensor circuit in the sensor module and demodulates and stores absolute pressure and temperature data derived from signals generated by the sensor circuit.
  • the sensor module is formed with a pickoff capacitor that changes capacitance with pressure changes and a reference capacitor that is relatively insensitive to pressure changes.
  • Sampled and stored blood pressure data are absolute pressure values and do not account for changes in barometric pressure affecting the ambient pressure load on the pressure sensor module.
  • the measured absolute pressure values must be compensated by separately recorded atmospheric pressure values.
  • US-5, 615,684 discloses a medical device for detecting hemodynamic conditions of a heart, comprising a pressure sensor place in the right ventricle and can consist of e.g. a piezoelectric crystal.
  • Pressure measurement with a piezocrystal is a fast, well-tried measurement method, which supplies easily interpreted measurement values.
  • the object of the present invention is to determine a signal representative of the intravascular static pressure, in the following referred to as "intravascular static pressure", related to the atmospheric pressure outside the body without measuring the atmospheric pressure.
  • a sensed short-term dynamic pressure signal in a pressure processing means the intravascular static pressure signal is determined.
  • short-term is meant herein a low number of heart-cycles (less than 10) continuously measured in the frequency range 0- 100 Hz.
  • the present invention is especially advantageous when processing a dynamic pressure signal obtained by a piezo- electric sensor.
  • the intravascular static pressure determined according to the present invention is defined as the static pressure inside the vascular system in relation to the barometric (atmospheric) pressure outside the body and is determined, according to the present invention, without using a pressure sensor outside the body. The difference between the intravascular static pressure and the barometric pressure is estimated.
  • the intravascular static pressure as used in the present application must not be mixed up with the absolute pressure related to the pressure in vacuum.
  • a further object achieved by the present invention is that in a medical device, e.g. an implantable heart stimulator, provided with a dynamic pressure sensor, in addition to a dynamic pressure signal, also is generated an intravascular static pressure signal.
  • FIG. 1 is a block diagram of the pressure measurement means according to the invention
  • Figures 2a-2e show waveforms illustrating the present invention
  • Figure 3 is a block diagram of an implantable medical device according to a preferred embodiment of the present invention.
  • Figure 4 discloses a schematic block-diagram of a pressure measurement arrangement according to prior art.
  • Figures 5a and 5b show different waveforms of the pressure measurement arrangement shown in figure 4.
  • Absolute pressure (static or dynamic): The pressure related to the atmospheric pressure. It should be noted that this is the conventional definition of absolute pressure in the medical field. In other technical field the absolute pressure may be defined as the pressure related to the pressure in vacuum.
  • Intravascular static pressure The pressure in a blood vessel related to the atmospheric pressure.
  • Dynamic pressure The short-term pressure obtained in a blood vessel or in the heart related to the ambient static pressure (long-term) in the blood vessel or the heart.
  • the implantable medical device comprises a pressure measurement means 2 arranged to receive signals 4 obtained by an intravascularly placed dynamic pressure sensor (not shown) sensing short-term pressure variations in a predetermined intravascular location.
  • an intravascularly placed dynamic pressure sensor (not shown) sensing short-term pressure variations in a predetermined intravascular location.
  • the dynamic pressure sensor may be arranged inside a heart on a specially dedicated lead or, preferable, as an integral part of a heart stimulation electrode lead.
  • the invention is not limited to perform measurements inside the heart, but the pressure measurements according to the claimed invention may be performed at any location in the intravascular/ circulatory system.
  • the dynamic pressure sensor is a piezo-electric sensor adapted to obtain a short-term dynamic (pulsatile) pressure in the heart or blood vessel.
  • the invention is applicable when using any type of pressure sensor generating a dynamic pressure signal. Among those may specifically be mentioned: piezo-electric pressure sensors, absolute pressure sensors, capacity pressure sensors, pressure sensors using membranes.
  • the signal 4 from the sensor is applied to a pressure transducer interface 6 in the pressure measurement means 2.
  • the pressure transducer interface 6 contains signal conditioning means in order to provide an electrical output that is representative of the sensed pressure. This output can be in analog or digital form.
  • the piezo-electric sensor is connected to a charge amplifier that provides an analog output.
  • the pressure transducer interface may also contain filtering means, for instance a lowpass filter to suppress high frequency disturbances. It may also contain an analog to digital converter for sampling of the analog sensor value. In this case signal 8 is a digital representation of the measured pressure.
  • the output from the transducer interface 6 is a dynamic pressure signal 8 that is applied to a pressure processing means 10 arranged in said pressure measurement means.
  • the pressure processing means 10 determines an intravascular static pressure signal 12 representing the pressure in the predetermined location inside the body in relation to the atmospheric pressure.
  • the dynamic pressure signal 8 is the only sensed signal used to determine the intravascular static pressure signal 12.
  • the pressure processing means 10 comprises filtering means 14, rectifying means 16, averaging means 18 and scaling means 20.
  • the filtering means includes a band-pass filter provided with a predetermined band-pass characteristic, where the lower border frequency preferably is in the range of 0,05-5 Hz and the upper border frequency preferably is in the range of 30-70 Hz, that inter alia suppresses low frequency parts of the measured signal.
  • the filtering means includes, in addition to the band-pass filter, a processing block, e.g. a second filter where the filter characteristics may be controlled by other sensed parameters, e.g. heart rate information.
  • a processing block e.g. a second filter where the filter characteristics may be controlled by other sensed parameters, e.g. heart rate information.
  • the rectifying means may be implemented by using either analogue (conventional circuitry comprising diodes and operational amplifiers) or digital technique (by determining the absolute value).
  • the averaging means is implemented by using either analogue or digital technique.
  • the average value is determined during a time interval from e.g. 2 up to 10 seconds.
  • low-pass filters are used and in the digital realisation detected values are added together and divided by a suitable value.
  • An analogue realisation of the scaling means 20 is achieved by amplifying the signal by a calibration factor.
  • a digital realisation is achieved by multiplying the signal by calibration factor(s).
  • the calibration factor may be determined in many different ways.
  • One way is to measure the pressure on the sensor when the patient is standing and lying, respectively and to determine the blood column in these two positions. The difference in heights of the blood column of the two positions corresponds to a pressure difference and a calibration factor may then be determined.
  • Figures 2a-2e show signal representations in different stages of the signal processing performed by the pressure measurement means 2. The horizontal axis of each of the disclosed curves represents the time in seconds and the vertical axis represents the pressure amplitude in mmHg.
  • the signal disclosed in figure 2a is the output from the pressure transducer interface 6, i.e. the dynamic pressure signal 8.
  • the signal disclosed in figure 2b is the output from the filtering means 14, i.e. the band-pass filtered dynamic pressure signal.
  • the signal disclosed in figure 2c is the output from the rectifying means 16, i.e. the rectified band-pass filtered dynamic pressure signal.
  • the signal disclosed in figure 2d is the output from the averaging means
  • the signal disclosed in figure 2e is the output from the scaling means 20, where the average signal from the averaging means is scaled.
  • the output from the scaling means is the intravascular static pressure signal 12.
  • the pressure measurement means 2 is arranged in an implantable heart stimulator, e.g. a conventional pacemaker, an implantable cardioverter/defibrillator or any heart- stimulating device.
  • an implantable heart stimulator 22 comprises the pressure measurement means 2, a detecting means 24 and a heart stimulator control means 26.
  • the heart stimulator naturally also comprises e.g. battery means.
  • the heart stimulator stimulates the heart via one or many heart electrode leads 28 usually inserted into the heart, so called intracardial electrode leads, or attached on the epicardium of the heart, so called epicardial leads.
  • the leads are provided with one or many stimulation surfaces arranged in contact with the tissue to be stimulated.
  • the electrode leads are also arranged to sense electrical heart events. Both stimulation and sensing are controlled by the heart stimulator control means 26 via control lines 30,32.
  • the control means 26 also controls control lines 34,36 the pressure measurement means 10, and in particular the processing block of the filtering means 14, and the detecting means 24.
  • the intravascular static pressure signal 12 is applied to the control means 26 and may be used to control the generation of stimulation pulses.
  • the sensed dynamic pressure signal 8 may be used, in addition to the determined intravascular static pressure signal 12, to control the generation of stimulation pulses.
  • the determined intravascular static pressure signal 12 is applied to the detecting means 24 that is arranged to identify predefined changes of the intravascular static pressure signal indicating predetermined hemodynamic conditions.
  • the detecting means may be adapted to indicate many different hemodynamic conditions. Among those may especially be mentioned: Congestive heart failure, separation of hemodynamically acceptable and non-acceptable AV-interval, separation of different flow in the coronary vessels of the heart and indication of asynchronously working heart stimulators.
  • the detecting means includes e.g. means to perform integration or differentiation (determining dp/dt) of different parts of the pressure signal curve and means to perform pattern recognition of the pressure signal curve in order to identify morphologies related to pathological states.
  • the dynamic pressure signal may be applied to the detecting means and may be used, in addition to the determined intravascular static pressure signal, to indicate predetermined hemodynamic conditions.
  • Figure 4 discloses a schematic block-diagram of a comparative test pressure measurement arrangement adapted to measure "true" intravascular absolute pressure, i.e. the pressure related to the pressure outside the body.
  • the arrangement comprises a pressure sensor 50, e.g. inserted into a heart, and connected to a pressure transducer 52.
  • the pressure transducer receives a sensed pressure signal, processes it and generates a processed signal that represents the absolute pressure which is applied to an averaging means 54 where a floating average of the processed signal is determined.
  • averaging means 54 where a floating average of the processed signal is determined.
  • FIG 5a the waveform of the output of the pressure transducer is shown and in figure 5b the waveform of the output of the averaging means is shown.
  • each of the disclosed curves represents the time in seconds and the vertical axis represents the pressure amplitude in mmHg.
  • the waveform shown in figure 5b representing the "true" absolute pressure should be compared to the waveform shown in figure 2e which is determined according to the present invention. As can be seen the two waveforms are very similar.
  • the present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

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  • Heart & Thoracic Surgery (AREA)
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  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
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Abstract

Implantable medical device comprising pressure measurement means (2) arranged to receive a signal (4) from an intravascularly placed dynamic pressure sensor sensing short-term pressure variations in a predetermined intravascular location. The sensed dynamic pressure signal is applied to a pressure processing means (10) in said pressure measurement means. The pressure processing means determines an intravascular static pressure signal (12) representing the pressure in said predetermined location in relation to atmospheric pressure, wherein said dynamic pressure signal is the only sensed signal used to determine said intravascular static pressure signal.

Description

Impl antable medi cal devi ce wi th pressure measurement means
Field of the invention The invention relates to an implantable medical device according to the preambles of the independent claims.
Background of the invention
An absolute pressure sensor is disclosed in US-5,535,752. The disclosed sensor is a capacitive type of sensor. An implantable lead having a sensor module formed in its distal end is coupled to a monitor that powers a sensor circuit in the sensor module and demodulates and stores absolute pressure and temperature data derived from signals generated by the sensor circuit. The sensor module is formed with a pickoff capacitor that changes capacitance with pressure changes and a reference capacitor that is relatively insensitive to pressure changes.
Sampled and stored blood pressure data are absolute pressure values and do not account for changes in barometric pressure affecting the ambient pressure load on the pressure sensor module. The measured absolute pressure values must be compensated by separately recorded atmospheric pressure values.
US-5, 615,684 discloses a medical device for detecting hemodynamic conditions of a heart, comprising a pressure sensor place in the right ventricle and can consist of e.g. a piezoelectric crystal. Pressure measurement with a piezocrystal is a fast, well-tried measurement method, which supplies easily interpreted measurement values.
The object of the present invention is to determine a signal representative of the intravascular static pressure, in the following referred to as "intravascular static pressure", related to the atmospheric pressure outside the body without measuring the atmospheric pressure. Summary of the invention
The above-mentioned objects are achieved according to the medical device provided with the features set forth in the independent claims.
Thus, by processing a sensed short-term dynamic pressure signal in a pressure processing means the intravascular static pressure signal is determined. By short-term is meant herein a low number of heart-cycles (less than 10) continuously measured in the frequency range 0- 100 Hz.
The present invention is especially advantageous when processing a dynamic pressure signal obtained by a piezo- electric sensor.
The intravascular static pressure determined according to the present invention is defined as the static pressure inside the vascular system in relation to the barometric (atmospheric) pressure outside the body and is determined, according to the present invention, without using a pressure sensor outside the body. The difference between the intravascular static pressure and the barometric pressure is estimated.
The intravascular static pressure as used in the present application must not be mixed up with the absolute pressure related to the pressure in vacuum.
A further object achieved by the present invention is that in a medical device, e.g. an implantable heart stimulator, provided with a dynamic pressure sensor, in addition to a dynamic pressure signal, also is generated an intravascular static pressure signal. Short description of the appended drawings
Figure 1 is a block diagram of the pressure measurement means according to the invention,
Figures 2a-2e show waveforms illustrating the present invention, Figure 3 is a block diagram of an implantable medical device according to a preferred embodiment of the present invention.
Figure 4 discloses a schematic block-diagram of a pressure measurement arrangement according to prior art.
Figures 5a and 5b show different waveforms of the pressure measurement arrangement shown in figure 4.
Detailed description of preferred embodiments of the invention In the present application it is referred to different pressures. These different pressures are defined herein according to the following:
Absolute pressure (static or dynamic): The pressure related to the atmospheric pressure. It should be noted that this is the conventional definition of absolute pressure in the medical field. In other technical field the absolute pressure may be defined as the pressure related to the pressure in vacuum.
Intravascular static pressure: The pressure in a blood vessel related to the atmospheric pressure.
Dynamic pressure: The short-term pressure obtained in a blood vessel or in the heart related to the ambient static pressure (long-term) in the blood vessel or the heart.
With references to figure 1 , the implantable medical device comprises a pressure measurement means 2 arranged to receive signals 4 obtained by an intravascularly placed dynamic pressure sensor (not shown) sensing short-term pressure variations in a predetermined intravascular location. As will be discussed below in relation with the description of a preferred embodiment of the invention the dynamic pressure sensor may be arranged inside a heart on a specially dedicated lead or, preferable, as an integral part of a heart stimulation electrode lead. However, the invention is not limited to perform measurements inside the heart, but the pressure measurements according to the claimed invention may be performed at any location in the intravascular/ circulatory system.
According to a preferred embodiment of the present invention, the dynamic pressure sensor is a piezo-electric sensor adapted to obtain a short-term dynamic (pulsatile) pressure in the heart or blood vessel. However, the invention is applicable when using any type of pressure sensor generating a dynamic pressure signal. Among those may specifically be mentioned: piezo-electric pressure sensors, absolute pressure sensors, capacity pressure sensors, pressure sensors using membranes.
As shown in figure 1 the signal 4 from the sensor is applied to a pressure transducer interface 6 in the pressure measurement means 2. The pressure transducer interface 6 contains signal conditioning means in order to provide an electrical output that is representative of the sensed pressure. This output can be in analog or digital form.
In the preferred embodiment the piezo-electric sensor is connected to a charge amplifier that provides an analog output. The pressure transducer interface may also contain filtering means, for instance a lowpass filter to suppress high frequency disturbances. It may also contain an analog to digital converter for sampling of the analog sensor value. In this case signal 8 is a digital representation of the measured pressure.
The output from the transducer interface 6 is a dynamic pressure signal 8 that is applied to a pressure processing means 10 arranged in said pressure measurement means. The pressure processing means 10 determines an intravascular static pressure signal 12 representing the pressure in the predetermined location inside the body in relation to the atmospheric pressure. The dynamic pressure signal 8 is the only sensed signal used to determine the intravascular static pressure signal 12.
The pressure processing means 10 comprises filtering means 14, rectifying means 16, averaging means 18 and scaling means 20.
The filtering means includes a band-pass filter provided with a predetermined band-pass characteristic, where the lower border frequency preferably is in the range of 0,05-5 Hz and the upper border frequency preferably is in the range of 30-70 Hz, that inter alia suppresses low frequency parts of the measured signal.
According to an alternative embodiment of the invention the filtering means includes, in addition to the band-pass filter, a processing block, e.g. a second filter where the filter characteristics may be controlled by other sensed parameters, e.g. heart rate information.
The rectifying means may be implemented by using either analogue (conventional circuitry comprising diodes and operational amplifiers) or digital technique (by determining the absolute value).
The averaging means is implemented by using either analogue or digital technique. The average value is determined during a time interval from e.g. 2 up to 10 seconds. In the analogue realisation low-pass filters are used and in the digital realisation detected values are added together and divided by a suitable value. An analogue realisation of the scaling means 20 is achieved by amplifying the signal by a calibration factor. A digital realisation is achieved by multiplying the signal by calibration factor(s).
The calibration factor may be determined in many different ways. One way is to measure the pressure on the sensor when the patient is standing and lying, respectively and to determine the blood column in these two positions. The difference in heights of the blood column of the two positions corresponds to a pressure difference and a calibration factor may then be determined. Figures 2a-2e show signal representations in different stages of the signal processing performed by the pressure measurement means 2. The horizontal axis of each of the disclosed curves represents the time in seconds and the vertical axis represents the pressure amplitude in mmHg. The signal disclosed in figure 2a is the output from the pressure transducer interface 6, i.e. the dynamic pressure signal 8.
The signal disclosed in figure 2b is the output from the filtering means 14, i.e. the band-pass filtered dynamic pressure signal.
The signal disclosed in figure 2c is the output from the rectifying means 16, i.e. the rectified band-pass filtered dynamic pressure signal.
The signal disclosed in figure 2d is the output from the averaging means
18, where the average of the rectified signal from the rectifying means is determined.
The signal disclosed in figure 2e is the output from the scaling means 20, where the average signal from the averaging means is scaled. The output from the scaling means is the intravascular static pressure signal 12.
According to a preferred embodiment of the invention the pressure measurement means 2 is arranged in an implantable heart stimulator, e.g. a conventional pacemaker, an implantable cardioverter/defibrillator or any heart- stimulating device. With references to figure 3 the implantable heart stimulator 22 comprises the pressure measurement means 2, a detecting means 24 and a heart stimulator control means 26.
Only means directly involved in the application of the present invention are disclosed in figure 3. The heart stimulator naturally also comprises e.g. battery means.
The heart stimulator stimulates the heart via one or many heart electrode leads 28 usually inserted into the heart, so called intracardial electrode leads, or attached on the epicardium of the heart, so called epicardial leads. The leads are provided with one or many stimulation surfaces arranged in contact with the tissue to be stimulated. The electrode leads are also arranged to sense electrical heart events. Both stimulation and sensing are controlled by the heart stimulator control means 26 via control lines 30,32.
The control means 26 also controls control lines 34,36 the pressure measurement means 10, and in particular the processing block of the filtering means 14, and the detecting means 24.
The intravascular static pressure signal 12 is applied to the control means 26 and may be used to control the generation of stimulation pulses.
According to a preferred embodiment the sensed dynamic pressure signal 8 may be used, in addition to the determined intravascular static pressure signal 12, to control the generation of stimulation pulses.
The determined intravascular static pressure signal 12 is applied to the detecting means 24 that is arranged to identify predefined changes of the intravascular static pressure signal indicating predetermined hemodynamic conditions.
The detecting means may be adapted to indicate many different hemodynamic conditions. Among those may especially be mentioned: Congestive heart failure, separation of hemodynamically acceptable and non-acceptable AV-interval, separation of different flow in the coronary vessels of the heart and indication of asynchronously working heart stimulators.
The detecting means includes e.g. means to perform integration or differentiation (determining dp/dt) of different parts of the pressure signal curve and means to perform pattern recognition of the pressure signal curve in order to identify morphologies related to pathological states.
Also the dynamic pressure signal may be applied to the detecting means and may be used, in addition to the determined intravascular static pressure signal, to indicate predetermined hemodynamic conditions.
Figure 4 discloses a schematic block-diagram of a comparative test pressure measurement arrangement adapted to measure "true" intravascular absolute pressure, i.e. the pressure related to the pressure outside the body. The arrangement comprises a pressure sensor 50, e.g. inserted into a heart, and connected to a pressure transducer 52. The pressure transducer receives a sensed pressure signal, processes it and generates a processed signal that represents the absolute pressure which is applied to an averaging means 54 where a floating average of the processed signal is determined. In figure 5a the waveform of the output of the pressure transducer is shown and in figure 5b the waveform of the output of the averaging means is shown. As in figures 2a-2e the horizontal axis of each of the disclosed curves represents the time in seconds and the vertical axis represents the pressure amplitude in mmHg. The waveform shown in figure 5b representing the "true" absolute pressure should be compared to the waveform shown in figure 2e which is determined according to the present invention. As can be seen the two waveforms are very similar. The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

Claims
1. Implantable medical device comprising pressure measurement means (2) arranged to receive a signal (4) from an intravascularly placed dynamic pressure sensor sensing short-term pressure variations in a predetermined intravascular location, characterized in that the sensed dynamic pressure signal is applied to a pressure processing means (10) in said pressure measurement means, said pressure processing means determines an intravascular static pressure signal (12) representing the pressure in said predetermined location in relation to atmospheric pressure, wherein said dynamic pressure signal is the only sensed signal used to determine said intravascular static pressure signal.
2. Medical device according to claim 1, characterized in that the dynamic pressure sensor is a piezoelectric sensor.
3. Medical device according to claims 1 or 2, characterized in that the pressure processing means (10) comprises filtering means (14), rectifying means (16), averaging means (18) and scaling means (20).
4. Medical device according to claim 3, characterized in that said filtering means comprises a band-pass filter having a band-pass with a lower border frequency in the range of 0,05-5 Hz and the upper border frequency in the range of 30-70 Hz.
5. Medical device according to claim 1, characterized in that said device is an implantable heart stimulator.
6. Medical device according to claim 5, characterized in that said intravascular static pressure signal is used to control the generation of stimulation pulses.
7. Medical device according to claim 5 or 6, characterized in that said device comprises detecting means (12) arranged to identify predefined changes of the intravascular static pressure signal indicating predetermined hemodynamic conditions.
8. Medical device according to claim 7, characterized in that the sensed dynamic pressure signal is applied to said detecting means and is used, in addition to the determined intravascular static pressure signal, to indicate predetermined hemodynamic conditions.
9. Medical device according to any of claims 6-8, characterized i n that said filtering means (14) comprises an adaptive filter with a filter characteristic controlled by parameters related to the heart rate.
10. Medical device according to any of claims 6-9, characterized i n that the determined intravascular static pressure signal is used to control the generation of stimulation pulses.
11. Medical device according to claim 10, characterized in that the sensed dynamic pressure signal is used, in addition to the determined intravascular static pressure signal, to control the generation of stimulation pulses.
12. Method in an implantable medical device provided with a pressure measurement means arranged to receive a signal from an intravascularly placed dynamic pressure sensor sensing short-term pressure variations in a predetermined intravascular location, characterized in that said method comprises the following steps:
A) applying the sensed dynamic pressure signal to a pressure processing means,
B) determining an intravascular static pressure signal representing the pressure in said predetermined location in relation to atmospheric pressure, wherein said dynamic pressure signal is the only sensed signal used.
13. Method according to claim 1, characterized in that said determining step B comprises the following sub-steps:
Bl) filtering the applied sensed dynamic pressure signal in a band-pass filter having predetermined characteristics, B2) rectifying the filtered signal from step B 1 , B3) averaging the rectified signal from step B2, and B4) scaling the averaged signal from step B3.
PCT/SE2001/002150 2000-10-06 2001-10-03 Implantable medical device with pressure measurement means WO2002028478A1 (en)

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EP2397185A1 (en) 2010-06-18 2011-12-21 St. Jude Medical AB Blood pressure measurement with implantable medical device
US8209031B1 (en) 2007-04-05 2012-06-26 Pacesetter, Inc. Implantable lead for measuring physiologic information

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WO1990008502A1 (en) * 1989-01-30 1990-08-09 Martin Goffman Associates Fiber optic intravascular blood pressure transducer
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8209031B1 (en) 2007-04-05 2012-06-26 Pacesetter, Inc. Implantable lead for measuring physiologic information
EP2397185A1 (en) 2010-06-18 2011-12-21 St. Jude Medical AB Blood pressure measurement with implantable medical device

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