Ventricular crosstalk sensed in the atrial channel

In this patient, the diagnosis of crosstalk is obvious. The sensed ancillary atrial signal is of low amplitude and very precocious in relation to ventricular pacing. This tracing allows highlighting the peculiarities of post-ventricular atrial refractory periods. On the first tracing, oversensing of ventricular depolarization occurs during the PVARP. If the patient's atrial rhythm accelerates (upon exertion, for example), the atrial rate measured by the pacemaker (which includes the cycles during the PVARP) exceeds the fallback rate, which causes inappropriate mode switching. The first option is to prolong the far-field protection period. This is a refractory period applied in the atrium after ventricular sensing and pacing in order to avoid crosstalk. It is not truly absolute since a sensed signal is highlighted on the chain of markers and is denoted as Ars (FFP). On the other hand, this signal does not trigger an AV delay and is not integrated in the counter used for the diagnosis of atrial arrhythmias, thus avoiding inappropriate switching. The nominal value is 100 ms (programmable between 100 and 220 ms) after a spontaneous ventricular event and 150 ms (programmable between 100 and 220 ms) after a paced ventricular event.

When the crosstalk cannot be corrected by a suitable adjustment of the refractory periods, it is possible to modify atrial sensitivity while attempting to maintain a sufficient margin for the sensing of atrial signals in both sinus rhythm and arrhythmia. In this patient, the simplest approach is to program the Vp suppression mode that allows the recovery of a spontaneous conduction and thus avoids crosstalk.