Apparatus and method of arrhythmia detection in a subcutaneous implantable cardioverter/defibrillator

• US 20040236379A1
• Filed: 06/08/2004
• Published: 11/25/2004
• Est. Priority Date: 11/21/2001
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Ostroff, Alan H., Rissmann, William J., Bardy, Gust H., Allavatam, Venugopal, Erlinger, Paul J.
• Granted Patent: US 7,379,772 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3931 Protecting, e.g. back-up systems
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

In a subcutaneous implantable cardioverter/defibrillator, cardiac arrhythmias are detected to determine necessary therapeutic action. Cardiac signal information is sensed from far field electrodes implanted in a patient. The sensed cardiac signal information is then amplified and filtered. Parameters such as rate, QRS pulse width, cardiac QRS slew rate, amplitude and stability measures of these parameters from the filtered cardiac signal information are measured, processed and integrated to determine if the cardioverter/defibrillator needs to initiate therapeutic action.

Claims

1. A method of monitoring cardiac function of a patient in an implantable cardiac treatment system, the method comprising:

obtaining a cardiac rate for the patient from electrodes spaced apart and subcutaneously implanted in the patient;

determining whether the cardiac rate;

(a) exceeds a first threshold but does not exceed a second threshold;

or;

(b) exceeds the second threshold; and

;

if the cardiac rate exceeds the second threshold, directing therapy to the heart;

or

if the cardiac rate exceeds the first threshold but does not exceed the second threshold, directing further analysis to determine whether therapy is indicated.

2. The method of claim 1, wherein therapy is delivered using the same electrodes used for capturing a signal for obtaining the cardiac rate.

3. The method of claim 1, wherein the second threshold includes both a rate threshold and a time threshold, wherein the second threshold is exceeded if the cardiac rate exceeds the rate threshold for a period of time in excess of the time threshold.

4. The method of claim 1, wherein, if the cardiac rate does not exceed the first threshold, therapy is withheld.

5. The method of claim 1, wherein:

the step of performing further analysis includes receiving a signal corresponding to a portion of a cardiac complex and analyzing the signal using a microprocessor; and

if the cardiac rate does not exceed the first threshold, the signal is not analyzed by the microprocessor.

6. The method of claim 1, wherein the first threshold is set to about 140 bpm.

7. The method of claim 1, wherein the step of directing therapy to the heart includes charging a capacitor system and delivering a shock between first and second subcutaneously implanted electrodes disposed exclusive of the patient'"'"'s heart.

8. A cardiac rhythm management device comprising:

an implantable canister housing operational circuitry; and

a lead electrode assembly having at least one electrode disposed thereon;

wherein the operational circuitry is configured to perform the steps of;

obtaining a cardiac rate for the patient using implanted electrodes disposed exclusive of the patient'"'"'s heart;

determining whether the cardiac rate;

(a) exceeds a first threshold but does not exceed a second threshold;

or;

(b) exceeds the second threshold; and

;

if the cardiac rate exceeds the second threshold, directing therapy to the heart;

or

if the cardiac rate exceeds the first threshold but does not exceed the second threshold, directing further analysis to determine whether therapy is indicated.

9. The cardiac rhythm management device of claim 8, wherein the operational circuitry is configured such that the step of directing therapy includes delivering an electric shock between the same electrodes used to obtain the cardiac rate.

10. The cardiac rhythm management device of claim 8, wherein the operation circuitry is configured such that the second threshold includes both a rate threshold and a time threshold, wherein the second threshold is exceeded if the cardiac rate exceeds the rate threshold for a period of time in excess of the time threshold.

11. The cardiac rhythm management device of claim 8, wherein the operational circuitry is configured such that, if the cardiac rate does not exceed the first threshold, therapy is withheld.

12. The cardiac rhythm management device of claim 8, wherein the operational circuitry is configured such that:

the step of performing further analysis includes receiving a signal corresponding to a portion of a cardiac complex and analyzing the signal using a microprocessor; and

if the cardiac rate does not exceed the first threshold, the signal is not analyzed by the microprocessor.

13. The cardiac rhythm management device of claim 8, wherein the operational circuitry is configured such that the first threshold is set to about 140 bpm.

14. The cardiac rhythm management device of claim 8, wherein the operational circuitry is configured such that the step of directing therapy to the heart includes charging a capacitor system and delivering a shock between first and second implanted electrodes disposed exclusive of the patient'"'"'s heart.

15. A method of operating an implantable cardiac treatment system, the method comprising:

obtaining a cardiac rate for a patient using two implanted electrodes disposed outside of the heart and vasculature of the patient;

determining whether the cardiac rate;

(a) exceeds a first threshold but does not exceed a second threshold;

or;

(b) exceeds the second threshold; and

;

if the cardiac rate exceeds the second threshold, directing therapy to the heart;

or

if the cardiac rate exceeds the first threshold but does not exceed the second threshold, directing further analysis to determine whether therapy is indicated.

16. The method of claim 15, wherein the step of directing therapy to the heart includes:

charging a capacitive network to a desired voltage; and

discharging the capacitive network between shocking electrodes disposed outside of the heart and vasculature of the patient, at least one of the shocking electrodes being disposed on a canister containing operational circuitry for operating the system.

17. The method of claim 16, wherein the second threshold includes both a rate threshold and a time threshold, wherein the second threshold is exceeded if the cardiac rate exceeds the rate threshold for a period of time in excess of the time threshold.

18. The method of claim 16, wherein:

the step of performing further analysis includes receiving a signal corresponding to a portion of a cardiac complex and analyzing the signal using a microprocessor; and

if the cardiac rate does not exceed the first threshold, the signal is not analyzed by the microprocessor.

19. The method of claim 16, wherein the first threshold is set to about 140 bpm.

20. The method of claim 16, wherein:

the second threshold includes both a rate threshold and a time threshold such that the second threshold is exceeded if the cardiac rate exceeds the rate threshold for a period of time in excess of the time threshold;

if the cardiac rate does not exceed the first threshold, therapy is withheld;

the step of performing further analysis includes receiving a signal corresponding to a portion of a cardiac complex and analyzing the signal using a microprocessor; and

if the cardiac rate does not exceed the first threshold, the signal is not analyzed by the microprocessor.