Method and apparatus for improving the probability of success of defibrillation shocks

• US 6,154,672 A
• Filed: 12/14/1998
• Issued: 11/28/2000
• Est. Priority Date: 06/22/1998
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories), Duke University
• Inventors: Pendekanti, Rajesh, Wolf, Patrick D.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/212,033
• Time in Patent Office: 715 Days
• Field of Search: 607/4, 607/5, 607/14
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• 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

A system and method for providing improved defibrillation thresholds. In one embodiment of the invention, following the detection of fibrillation, a pacing pulse train is applied to a pacing electrode placed in the low gradient region of the left ventricular freewall to capture the tissue. In one embodiment, a pacing rate of about 80-95% of the VF cycle length is applied to achieve capture. Once capture of the tissue of the critical region is achieved, a high energy shock is delivered when the captured tissue is in the process of activation. The defibrillation shock is delivered at the end of the pacing train, with a coupling interval of either about 80-95% of the pacing rate (i.e., about 64-90% of the VF cycle length), or, alternatively, about 5-20% of the pacing rate (i.e., about 4-19% of the VF cycle length). In an alternative embodiment of the invention, a sensing electrode array is placed in the low gradient region of the left ventricular freewall to monitor such time as a substantial percentage of the tissue of the low gradient region is in the process of activation, i.e., on the downstroke of the respective EGMs, and then delivering the defibrillation shock at that instant.

Claims

1. A method for delivering defibrillation therapy to a patient'"'"'s heart comprising the steps of:

(a) positioning a plurality of defibrillation electrodes in or near the patient'"'"'s heart;

(b) attaching at least one sensor in a low gradient region of a ventricle of the patient'"'"'s heart;

(c) monitoring the patient'"'"'s heart to detect the presence of a heart fibrillation;

(d) acquiring a respective real time ventricular unipolar electrogram from each said at least one sensor;

(e) monitoring each said electrogram until a percentage of greater than 50% of each said acquired electrogram is detected to be simultaneously in downstroke; and

(f) delivering a defibrillation shock to said heart fibrillation immediately upon the occurrence of step (e) effective to terminate fibrillation.

2. The method of claim 1, wherein said percentage represents a numerical value ranging from about 80% to 100%.

3. The method of claim 1, where said at least one sensor of steps (b), (d) and, (e) is a single sensor.

4. The method of claim 1, where said at least one sensor of steps (b), (d) and (e) is two separate sensors.

5. The method of claim 1, where said at least one sensor of steps (b), (e) and (f) is three or more separate sensors.

6. A method for delivering defibrillation therapy to a patient'"'"'s heart comprising the steps of:

(a) positioning a plurality of defibrillation electrodes in or near the heart;

(b) attaching a plurality of sensors in a low gradient region of a ventricle;

(c) monitoring the patient'"'"'s heart to detect the presence of a heart fibrillation;

(d) acquiring respective real time ventricular unipolar electrograms from said sensors;

(e) monitoring said electrograms for a first period of time to detect for a first condition in which all said acquired electrograms are simultaneously in downstroke;

(f) delivering a defibrillation shock to said heart fibrillation immediately upon an occurrence of said first condition during said first period of time, effective to terminate fibrillation;

(g) continuing monitoring of said electrograms to detect for a second condition in the event said first period of time elapses without the occurrence of said first condition, wherein the second condition occurs when a percentage of greater than 50% of acquired electrograms are detected to be simultaneously in downstroke; and

(h) delivering a defibrillation shock to said heart fibrillation immediately upon the occurrence of said second condition, effective to terminate fibrillation.

7. The method of claim 6, wherein said percentage represents a numerical value ranging from about 80% to 100%.

8. The method of claim 6, where said sensor are spaced about 1 cm apart from each other.

9. The method of claim 6, wherein said first period of time is about 2-4 seconds.

10. The method of claim 6, wherein the low potential gradient region is the left ventricle free wall region and the plurality of defibrillation electrodes have a defibrillation lead configuration of right ventricle to superior vena cava.

11. A cardiac therapy apparatus for treating a heart in need of ventricular defibrillation, comprising:

at least one sensor adapted to be positioned proximate a location in a low potential gradient region of a ventricle of the heart for generating electrogram signals;

a plurality of defibrillation electrodes capable of delivering a ventricular defibrillation (VDF) shock to said heart; and

signal processing circuitry for (i) receiving said electrogram signals from said at least one sensor, and (ii) being capable of detecting a ventricular fibrillation episode, and (iii) being capable of detecting when a percentage of greater than 50% of said electrogram signals are simultaneously in downstroke, and (iv) being capable of generating control signals for activating said electrodes such that said electrodes are capable of delivering the ventricular defibrillation shock when a percentage of greater than 50% of said electrogram signals are detected to be simultaneously in downstroke.