Defibrillator with improved hemodynamic response and enhanced myocardial stability

• US 6,096,061 A
• Filed: 06/12/1997
• Issued: 08/01/2000
• Est. Priority Date: 06/12/1997
• Status: Expired due to Term

• Current Assignee: Advanced Medical Optics Incorporated (Johnson & Johnson)
• Original Assignee: Intermedics Incorporated
• Inventors: Alt, Eckhard, Stotts, Lawrence J.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/874,032
• Time in Patent Office: 1,146 Days
• Field of Search: 607/4, 607/6, 607/17, 607/19, 607/21, 607/24, 607/25
• US Class Current: 607/4
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

An implantable medical interventional device responds to detection of any of a plurality of cardiac dysrhythmias in a human patient by performing an appropriate therapy which may include cardiac pacing, cardioversion or defibrillation according to the nature of the detected dysrhythmia. A first sensor detects whether and what type of dysrhythmia is occurring. A generator produces pulses and/or shocks for delivery to the patient'"'"'s heart according to whether a detected dysrhythmia is bradycardia or slow pathologic tachycardia on the one hand, or fast tachycardia or fibrillation on the other hand. An optimizer in the device at all times maintains a substantial match of the cardiac pacing rate to the hemodynamic needs of the implant patient under conditions of rest and physical activity; including sensing and distinguishing periods of patient physical activity and rest, and generating a signal representative thereof to control the cardiac pacing rate accordingly. In this way, the device focuses on correction of cardiac pacing problems before they become sufficiently aggravated to require more aggressive cardioversion and defibrillation therapies.

Claims

1. An implantable defibrillator adapted to deliver cardiac pacing, cardioversion and defibrillation therapies in selective response to dysrhythmia detection from an implant patient'"'"'s cardiac signal, the defibrillator comprising:

a sensor of the patient'"'"'s heart rate;

a cardioverter/defibrillator for producing electrical shocks of adjustable energy level to be applied to the patient'"'"'s heart in response to applicable detected levels of pathologic accelerated heart rate;

a rate controllable generator responsive to a pacing dysrhythmia sensed by said heart rate sensor for generating cardiac pacing pulses at a rate designed to correct said sensed dysrhythmia for application to the patient'"'"'s heart;

an optimizer for matching the cardiac pacing rate of said generator to the hemodynamic needs of the implant patient under conditions of rest and physical activity;

including sensing and distinguishing periods of patient physical activity and rest, and generating a signal representative thereof to control the cardiac pacing rate accordingly as well as according to the extent of activity; and

a processor for processing the control signal generated by the optimizer to enhance sensitivity and specificity thereof by detecting true physical activity of the patient and for applying the enhanced processed control signal to said rate controllable generator to appropriately adjust the pacing rate thereof;

whereby said defibrillator is adapted to suppress an acceleration of cardiac dysrhythmias by developing and delivering a pacing therapy that matches the patient'"'"'s hemodynamic needs.

2. The defibrillator of claim 1, wherein said optimizer comprises an accelerometer.

3. The defibrillator of claim 2, wherein the accelerometer is mounted within a case that houses electronic circuitry and other components of the defibrillator, and is isolated from pressure exerted external to the case.

4. The defibrillator of claim 2, further including a second, complementary sensor electrically coupled to electronic circuitry of the defibrillator for confirmation of the output signal of the accelerometer.

5. The defibrillator of claim 4, wherein the complementary sensor comprises means for sensing a physiological parameter representative of metabolic and hemodynamic needs of the patient other than physical activity, said parameter being selected from the group consisting of body temperature, minute ventilation, Q-T interval, and intracardiac phenomena.

6. The defibrillator of claim 1, wherein said processor includes a filter for passing substantially only components of the control signal in a frequency band below approximately 4 Hz.

7. The defibrillator of claim 6, wherein said filter performs bandpass filtering in a range between approximately 0.1 Hz and approximately 4.0 Hz.

8. The defibrillator of claim 6, wherein said optimizer comprises an accelerometer.

9. The defibrillator of claim 8, wherein said processor includes means for varying a baseline pacing rate to reflect a changed level of physical activity by the patient.

10. An implanted defibrillator device-implemented method of delivering cardiac pacing, cardioversion and defibrillation therapies in selective response to dysrhythmia detection an implant patient'"'"'s cardiac signal, said method comprising the steps of:

sensing the patient'"'"'s heart rate;

delivering cardioversion/defibrillation therapies by producing electrical shocks of adjustable energy level for application to the patient'"'"'s heart in response to applicable detected levels of pathologic accelerated heart rate;

responding to a pacing dysrhythmia in the sensed heart rate by generating cardiac pacing pulses designed to correct said dysrhythmia for application to the patient'"'"'s heart; and

optimizing a match between the generated cardiac pacing rate and the contemporaneous hemodynamic needs of the implant patient under conditions of rest and physical activity;

including sensing periods of patient physical activity and rest and generating a signal representative thereof to control the cardiac pacing rate accordingly and according to the extent of activity;

processing said control signal generated to enhance sensitivity and specificity thereof by detecting true physical activity, and using the enhanced processed control signal to control the pacing rate;

whereby to focus on correcting cardiac pacing problems before they become sufficiently aggravated to require more aggressive cardioversion and defibrillation therapies.

11. The method of claim 10, wherein the step of activity sensing is performed by an accelerometer.

12. The method of claim 11, including confirming the output signal of the accelerometer with a second, complementary sensor electrically coupled to electronic circuitry of the defibrillator.

13. The method of claim 12, including using the complementary sensor to sense a physiological parameter representative of metabolic and hemodynamic needs of the patient other than physical activity, said parameter being selected from the group consisting of body temperature, minute ventilation, Q-T interval, and intracardiac phenomena.

14. The method of claim 10, wherein the step of signal processing includes filtering said control signal to pass substantially only components thereof in a frequency band below approximately 4 Hz.

15. The method of claim 14, wherein the step of filtering comprises bandpass filtering in a range between approximately 0.1 Hz and approximately 4.0 Hz.

16. The method of claim 14, wherein the step of activity sensing is performed using an accelerometer.

17. The method of claim 16, wherein the step of signal processing includes varying a baseline pacing rate to reflect a changed level of physical activity of the patient.

18. An implantable medical interventional device for responding to detection of any of a plurality of cardiac dysrhythmias in a human patient by performing an appropriate therapy including cardiac pacing, cardioversion or defibrillation according to the nature of the detected dysrhythmia, said device comprising:

a first sensor for detecting any of said plurality of cardiac dysrhythmias;

a generator of pacing pulses and electrical shocks for delivery to the patient'"'"'s heart according to whether a detected dysrhythmia is bradycardia or a relatively slow pathologic tachycardia on the one hand, or a relatively fast tachycardia or fibrillation on the other hand; and

an optimizer for substantially matching the patient'"'"'s heart rate to hemodynamic demand under conditions of physical activity and rest of the patient, including;

a second sensor for sensing periods of patient activity and rest as imposing different hemodynamic demands on the patient'"'"'s cardiovascular system, and for producing a signal representative of applicable hemodynamic demand, and

a signal processor for enhancing said second sensor signal to detect true physical activity of the patient and the extent thereof, and for applying the enhanced processed signal to said generator to vary the pacing rate to conform to the patient'"'"'s hemodynamic demand;

whereby to focus on correction of cardiac pacing problems before they become sufficiently aggravated to require more aggressive cardioversion and defibrillation therapies.

19. The device of claim 18, wherein said second sensor comprises an accelerometer.

20. The device of claim 19, wherein said signal processor includes:

a bandpass filter for selectively passing signal components in a frequency band below about 4 Hz.

21. The device of claim 20, further including:

a third sensor for confirming or contesting the indications of exercise and rest sensed by said second sensor.

22. An implantable defibrillator-implemented method of delivering cardiac pacing, cardioversion and defibrillation therapies in selective response to dysrhythmia detection an implant patient'"'"'s cardiac signal, said method comprising the steps of:

sensing the patient'"'"'s heart rate;

providing a capability to deliver cardioversion/defibrillation therapies at least partially in the form of electrical shocks of adjustable energy level for application to the patient'"'"'s heart in response to detected extent of pathologic accelerated heart rate; and

optimizing a match between a generated cardiac pacing rate and contemporaneous hemodynamic needs of the implant patient by controlling the cardiac pacing rate according to detected conditions of physical activity and rest, to reduce the frequency at which the patient experiences pathologic accelerated heart rate sufficient to induce one or more of said electrical shocks.