Operation of the Vp suppression algorithm
Tracing
Manufacturer Biotronik
Device PM
Field Pacing Modes
N° 10
Patient
72-year-old man implanted with an Evia DR-T pacemaker for complete atrioventricular block; interrogation of the pacemaker; Vp suppression algorithm On.
Graph and trace
Tracing 10a
- atrial sensing and ventricular pacing with programmed AV delay;
- prolongation of the AV delay (450 ms) for 8 consecutive cycles with no observed spontaneous conduction;
- return to ventricular pacing with programmed AV delay.
Patient: 72-year-old man implanted with an Evia DR-T pacemaker for complete paroxysmal atrioventricular block; interrogation of the pacemaker.
Tracing 10b
- spontaneous atrial and ventricular rhythm;
- 3 out of 5 P waves blocked;
- switch to DDD mode;
- after 30 seconds, search for a spontaneous conduction with a prolongation of the AV delay to a value of 450 ms; spontaneous conduction;
- 6 consecutive intervals with spontaneous conduction; switch to ADI mode;
- 3 out of 5 P waves blocked;
- switch to DDD mode;
- pacing in DDD mode for 30 seconds;
- prolongation of the AV delay to a value of 450 ms for 8 cycles; for the first 3 cycles, appearance of spontaneous conduction;
- on the following cycles, ventricular pacing since absence of spontaneous conduction after 450 ms;
- continuation in DDD mode with programmed AV delay since absence of 6 consecutive cycles with spontaneous conduction.
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The various algorithms for avoiding right ventricular pacing differ in terms of criteria for switching from ADI mode to DDD mode but also in terms of criteria for re-switching to ADI mode. For BiotronikTM pacemakers, when the device is operating in DDD mode, it searches for the presence of an underlying self-paced rhythm every 30 seconds and subsequently spaces the latter (1, 2, 4, 8, 16 ... 128 minutes, up to 20 hours) if the search is inconclusive (persistence of impaired atrioventricular conduction). To achieve the latter, the pacemaker prolongs its AV delay to 450 ms for 8 cycles (identical duration for spontaneous or paced atrial activity). The pacemaker switches to ADI mode if 1 spontaneous ventricular event is sensed during this prolonged AV delay over 6 consecutive cycles (changeable nominal value). During this search, there can thus be no blocked P wave (if absence of spontaneous conduction, ventricular pacing after 450 ms). The episodic prolongation of the AV delay may, however, lead to the occurrence of PMT and can be problematic if it occurs during exercise with a risk of reaching the 2:1 point over a few cycles (depending on the sum of the AV delay + PVARP).
To avoid iterative alternations between DDD and ADI mode, the Vp suppression function is halted for 20 hours if more than 15 switches/hour are observed.