Crosstalk on the atrial channel

Post-ventricular atrial blanking is the first component of the post-ventricular atrial refractory period. Traditionally, no sensing was possible in a window identified as a blanking which constituted an absolute refractory period. On the new pacemaker platforms, this differentiation between blanking (absence of sensing and absence of visualization of the signal on the chain of markers) and refractory periods (sensing possible with visualization on the chain of markers) is less clear-cut. Indeed, according to the programming, an atrial event sensed during post-ventricular atrial "blanking" can be visualized on the chain of markers and interfere with the functioning of different algorithms. There are 3 programming options:

1. if the PVAB method is programmed to "absolute", the functioning is identical to the older pacemakers and the event does not appear on the marker chain;
2. if the PVAB method is programmed to "partial", it should be noted that the first 30 milliseconds correspond to an absolute blanking so as to avoid recording of the pacing spike; an atrial event occurring in the period after these 30 ms appears on the marker chain and is labeled Ab; this atrial event does not trigger an AV delay but is counted for atrial arrhythmia diagnostic purposes; atrial sensitivity is not altered;
3. if the PVAB method is programmed to "partial +", the functioning is identical to the previous setting except that after a sensed or paced ventricular event, the sensitivity is temporarily decreased to reduce the risk of crosstalk.

A signal detected in the PVAB (classified as Ab) likewise to a signal detected in the PVARP (classified as AR) does not trigger an AV delay but is counted for the diagnosis of atrial arrhythmias.

In this patient, the diagnosis of crosstalk is evident. The sensed supernumerary atrial signal is small in size and very precocious relative to the ventricular pacing. To avoid this crosstalk, 4 solutions can be envisioned:

1. reducing the amplitude of ventricular pacing and/or programming ventricular pacing in bipolar mode; these changes did not solve the problem in this patient; in fact, ventricular pacing was already set in bipolar mode; moreover, in the majority of cases, it is more ventricular depolarization (not influenced by pacing amplitude) than the ventricular pacing stimulus which is sensed by the atrial channel;
2. programming atrial sensing to bipolar mode which was also already the case;
3. reducing the programmed atrial sensitivity; the programming of a sensitivity at 0.5 mV (0.3 mV initially) allowed resolving the problem of oversensing; this modification of programming, however, would limit the sensing capability of an atrial fibrillation which is often associated with a dampening of the amplitude of the atrial signals;
4. changing the PVAB methodology; scheduling a long-term absolute blanking may solve the problem but exposes the patient to the risk of undersensing of atrial arrhythmia and particularly of an atrial flutter (risk of 2:1 flutter); in this patient, the programming of partial blanking + solved the problem, the pacemaker temporarily becoming less sensitive at the atrial channel following ventricular pacing.