Pacemaker system with inhibition of AV node for rate regulation during atrial fibrillation

• US 6,256,537 B1
• Filed: 03/17/1999
• Issued: 07/03/2001
• Est. Priority Date: 03/17/1999
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Van Dam, Peter, Smit, Josephus P. A., Stoop, Gustaaf A. P.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/270,796
• Time in Patent Office: 839 Days
• Field of Search: 607/4, 607/5, 607/9, 607/14
• US Class Current: 607/14
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

There is provided a system for regulating ventricular rate in the presence of abnormally high atrial rates, e.g., during episodes of atrial fibrillation. During such an episode, the system, preferably incorporated into an implantable pacemaker, applies subthreshold bursts of stimulus pulses to or proximate to the patient'"'"'s AV node so as to inhibit conduction of electrical signals through to the ventricle during the bursts. The bursts are timed in relation to the last conducted ventricular signal, and in terms of burst length, to provide a rate of conducted signals through the AV node which results in a substantially regular and reduced ventricular rate. During the inhibition mode of operation, the system monitors to determine the efficacy of inhibition, by tracking the percentage of ventricular senses that occur during the burst periods. When inhibition is found to be below an acceptable percentage, the system carries out an inhibition test and re-adjusts the burst parameters to provide bursts of optimized stimulation energy.

Claims

1. An implantable stimulus system for providing atrial defibrillation therapy to a patient'"'"'s heart, comprising:

atrial sense means for sensing atrial signals from the patient'"'"'s heart;

burst means for generating bursts of pulses, each said burst having a controllable burst period;

delivery means for delivering said bursts to the patients AV node; and

inhibiting means for controlling an amplitude of each said burst to be subthreshold to said AV node so as to inhibit cardiac conduction through said AV node during each said burst period.

2. The system as described in claim 1, further comprising:

ventricular sense means for sensing ventricular signals from the patient'"'"'s heart;

AF means for detecting an episode of atrial fibrillation;

burst period means operative following a detection of an episode of atrial fibrillation, for determining said burst period; and

burst control means for controlling said burst means to generate a said burst for a duration of said burst period following a sensed ventricular signal.

3. The system as described in claim 2, further comprising V—

V means for providing a V—

V interval for controlling the rate of ventricular contractions during said episode, and wherein said burst period means further comprises determining means for determining said burst period as a function of said V—

V interval.

4. The system as described in claim 2, wherein said burst period means further comprises start means for determining a start time of said burst period following a sensed ventricular signal.

5. The system as described in claim 4, wherein said start means further comprises first timing means for timing out said burst start time in reference to a sensed ventricular signal.

6. The system as described in claim 5, wherein said first timing means further comprises means for determining a ventricular refractory period following a sensed ventricular signal and for setting said burst start time at about the end of said refractory period.

7. The system as described in claim 4, further comprising means for determining a time interval between sensed ventricular signals, and wherein said start means comprises adjust means for adjusting said start time in a direction to minimize said burst period when said time interval is less than the combination of said burst period plus a patient AV interval.

8. The system as described in claim 1, further comprising threshold means for determining the patient inhibition threshold, and wherein said inhibiting means comprises adjust means for adjusting the level of said burst pulses to maintain inhibition of the patient'"'"'s AV node during each said burst.

9. The system as described in claim 8, further comprising ventricular sense means for sensing ventricular signals from the patient'"'"'s heart and interval means for determining an interval of successive ventricular signals, and wherein said threshold means comprises VS means for determining when ventricular signals occur at VV intervals indicating that said bursts are not inhibiting conduction of ventricular signals through the patient'"'"'s AV node.

10. The system as described in claim 9, wherein said VS means further comprises means for determining when a sensed ventricular signal has been conducted through the patient'"'"'s AV node during delivery of a said burst.

11. The system as described in claim 10, further comprising percentage means for determining a measure of the percentage of sensed ventricular signals which have been conducted during a said burst, and response means for adjusting at least one parameter of said burst as a function of said measure.

12. The system as described in claim 11, wherein said response means further comprises means for adjusting the amplitude of said burst pulses.

13. The system as described in claim 12, wherein said response means further comprises means for adjusting a frequency of said burst pulses.

14. The system as described in claim 1, further comprising timing means for timing the generation of said bursts relative to sensed atrial signals so as to limit the rate Of said atrial signals that can pass through the patient'"'"'s AV node to the patient'"'"'s ventricle.

15. The system as described in claim 14, further comprising burst period means for controlling said burst period so that said rate is limited to a predetermined ventricular rate.