Patient - EN
74-year-old man implanted with an Azure XT DR dual-chamber pacemaker for primary atrioventricular block and episodes of paroxysmal complete atrioventricular block; palpitations; recordings of a tachycardia with ventricular pacing; programming: maximal tracking rate of 130 bpm, AV delay due to spontaneous atrial activity of 250 ms.
Graph and trace
- ineffective atrial pacing followed by effective ventricular pacing;
- retrograde atrial conduction sensed outside the PVARP;
- onset of a PMT;
- eighth consecutive VP-AS intervals;
- prolongation of the AV delay of 50 ms (220 to 270 ms) over 1 interval;
- no significant change in the VP-AS interval (arguing in favor of a PMT and against the diagnosis of sinus tachycardia); pacing with unaltered AV delay;
- no significant change in the VP-AS interval; pacing with unaltered AV delay;
- prolongation of the AV delay of 50 ms (220 to 270 ms) over 1 interval;
- no significant change in the VP-AS interval; pacing with unaltered AV delay;
- no significant change in the VP-AS interval; pacing with unaltered AV delay;
- prolongation of the AV delay by 50 ms (220 to 270 ms) over 1 interval;
- no significant change in the VP-AS interval; pacing with unaltered AV delay;
- no significant change in the VP-AS interval; pacing with unaltered AV delay;
- diagnosis of PMT; prolongation of the PVARP to 400 ms; atrial signal sensed in the PVARP thus not triggering an AV delay;
- the PMT is terminated; ineffective atrial pacing;
- retrograde atrial conduction and immediate resumption of PMT.
NID old - EN
3308
This patient presented multiple episodes of PMT induced by a failure of atrial capture. A long AV delay was programmed to promote spontaneous conduction, which also increased the risk of initiating and maintaining a PMT. This tracing illustrates the specificity of the new anti-PMT algorithm available on the latest dual-chamber pacemaker platforms. This algorithm includes a confirmation phase with modification of the AV delay to affirm the diagnosis of PMT and to differentiate the latter from that of sinus tachycardia. After 8 consecutive VP-AS intervals, the AV delay is prolonged by 50 ms over one cycle; the VA interval is then measured as a result of this modification in AV delay over 2 consecutive intervals. If, despite this modification, the VA interval remains constant, a PMT is suspected (in the case of sinus tachycardia, atrial intervals are not altered by a change in AV delay; if the AV delay is prolonged over one interval, the VA interval is therefore shortened). This sequence is repeated 3 times (prolongation of the AV delay over one interval, followed by normal AV delay over 2 intervals). If analysis of the VA delays (VP-AS) is indicative of a PMT, the PVARP is prolonged to 400 ms over one interval for the next atrial event to be sensed in the refractory period. This refractory event is not synchronized to the ventricle during 1 interval and the tachycardia is terminated.
The objective of this new algorithm, with confirmation of the diagnosis of PMT before attempting to terminate the latter by prolonging the PVARP over one interval, is to increase the specificity and avoid inappropriate interventions during a sinus tachycardia which led to the occurrence of a blocked P wave which could be symptomatic and possibly arrhythmogenic during exertion.