Dual chamber pacemaker system with V-A time measurement apparatus and method

• US 4,515,161 A
• Filed: 01/10/1984
• Issued: 05/07/1985
• Est. Priority Date: 01/10/1984
• Status: Expired due to Term

• Current Assignee: Vitatron Medical BV (Medtronic Plc)
• Original Assignee: Vitafin N.V. (Medtronic Plc)
• Inventors: Boute, Willem, Wittkampf, Frederik H. M.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/569,669
• Time in Patent Office: 483 Days
• Field of Search: 128/419 PG, 128/419 PT
• US Class Current: 607/27
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

A dual chamber pacemaker having means for operating in different pacing modes, including dual chamber modes, contains the capability of switching into a fixed rate ventricular pacing mode and of sensing early atrial signals without affecting the ventricular pacing timing. The timing of a plurality of such sensed early atrial signals is analyzed to determine if they represent retrograde P waves and, if so, the indicated V-A conduction time. The pacemaker atrial refractory time is adjusted so that, during dual chamber operation, the atrial refractory time extends past the time of anticipated retrograde P waves, thereby optimizing the setting of the atrial refractory period for avoidance of pacemaker mediated tachycardia. Other pacing conditions may also be adjusted in response to the determined patient V-A time.

Claims

1. In a dual chamber cardiac pacemaker, a method of determining patient V-A conduction time and setting the pacemaker atrial refractory period as a consequence thereof, comprising the following steps:

(a) setting the patient'"'"'s pacemaker to a ventricular pacing mode and delivering ventricular stimulus signals at a first stable pacing rate;

(b) enabling atrial sensing during a predetermined A sense window of the pacing cycle;

(c) measuring the timing of sensed atrial signals relative to delivered ventricular stimulus signals;

(d) determining whether said timing is substantially stable, and determining V-A conduction time as a function of determined stable timing; and

(e) setting said atrial refractory period as a function of said determined V-A time, and returning the pacemaker to a selected mode of dual chamber operation.

2. The method as described in claim 1, wherein said ventricular pacing mode comprises the cyclical step of delivering of said ventricular stimulus signals independently of said atrial sensing.

3. The method as described in claim 2, further comprising the step of blanking atrial sensing at about the time of each delivered ventricular stimulus.

4. The method as described in claim 1, further comprising delivering ventricular stimulus signals at least a second stable pacing rate and determining V-A conduction time at said second stable rate, and setting said atrial refractory period as a function of the determined V-A conduction times.

5. The method as described in claim 1, wherein the step of enabling sensing during said A sense window is performed by externally programming the pacemaker.

6. The method as described in claim 1, wherein the method is carried out automatically by an implanted pacemaker.

7. Dual chamber pacemaker system apparatus, having means for sensing and pacing in both the atrium and ventricle, and means for operating in a plurality of pacing modes, comprising means for switching pacemaker operation into a fixed rate ventricular pacing mode;

means for sensing atrial signals during a predetermined sense window of the fixed rate pacing cycle;

means for measuring the timing of early atrial signals sensed within said sense window in relation to the pacing cycle;

means for determining as a function of said timing whether there is retrograde V-A conduction, and for determining the V-A time thereof; and

means for resetting the atrial refractory period as a function of said determined V-A conduction time and returning to a selected dual chamber mode of operation.

8. The apparatus as described in claim 7, wherein said pacemaker is an implantable pacemaker, and comprising programming means for selecting said fixed pacing mode.

9. The apparatus as described in claim 7, comprising means for changing the fixed pacing rate and determining V-A conduction time corresponding to each said fixed rate.

10. A dual chamber pacemaker system, having means for pacing and sensing in both the ventricle and atrium, and means for selecting the mode of operation, characterized by:

means for setting a fixed rate ventricular pacing mode;

means for sensing a plurality of atrial signals during a time such that they are likely to be other than natural P waves;

logic means for determining if said sensed atrial signals are retrograde P waves;

V-A means responsive to said logic means for determining the patient V-A conduction time from the timing of said sensed atrial signals when they are retrograde P waves; and

refractory means for setting the pacemaker atrial refractory period as a function of said determined V-A conduction time.

11. A method of determining patient V-A conduction time utilizing a programmable dual chamber pacemaker system, comprising:

setting said pacemaker into a ventricular pacing mode for pacing the ventricle by delivering stimuli independent of atrial signals;

enabling atrial sensing only during a predetermined sense window of the pacing cycle, and measuring the V-A times of atrial signals sensed during said window, said sense window being set to achieve blanking of atrial sensing at least during delivery of ventricular stimuli;

determining when said measured V-A times are substantially stable over a plurality of pacer cycles, and determining a patient V-A time as a function of said stable times; and

setting the atrial refractory period of said pacemaker system as a function of said determined V-A time.

12. An implantable dual chamber pacemaker system having means for pacing the patient in which it is implanted, comprising

retrograde conduction means for determining the presence of retrograde conduction in said patient and for determining retrograde conduction time, and

varying means for automatically varying an operating condition or parameter of said system in response to said determined retrograde conduction time.

13. The pacemaker system as described in claim 12, wherein said varying means varies the system atrial refractory period.

14. The pacemaker system as described in claim 12, wherein said varying means varies the pacing mode.