Patient - EN
77-year-old man, implanted with a triple-chamber defibrillator Consulta CRT-D for mitral valvular cardiomyopathy with left bundle branch block and long PR interval; routine follow-up 3 months after implantation; episodes of ventricular sensing are recorded; the right ventricular lead is implanted in the interventricular septum and is not displaced on chest X-ray.
Graph and trace
Episodes of ventricular sensed event in the device memory
- atrial and biventricular pacing (AP-BV);
- atrial pacing and sensing of two spontaneous ventricular events with a fixed coupling interval of 270-280ms; a ventricular premature beat with a short coupling interval is suspected.
Interrogation of the device and recording of the tracings; EGM1: Atrial EGM, EGM2: Ventricular EGM (bipolar channel), EGM3: Ventricular EGM (far-field channel); - atrial and biventricular pacing (AP-BV);
- atrial pacing and sensing of two spontaneous ventricular events; probable crosstalk: the atrial depolarization is sensed by the ventricular channel after the safety window (first VS marker); the second VS corresponds to the sensing of the spontaneous ventricular depolarization;
- decrease in ventricular sensitivity (from 0.3 to 0.5 mV);
- disappearance of the crosstalk.
NID old - EN
3102
This tracing shows a relatively rare case of loss of biventricular pacing after A/V crosstalk following atrial pacing. Atrial pacing initiates 2 periods of ventricular protection to avoid crosstalk: 1) a non-programmable post atrial paced ventricular blanking period (that lasts 30 ms on the new CRT-D platforms); during this time interval, no ventricular sensing is possible; 2) a safety window ending 110 ms after the atrial pacing; its duration is not programmable although it is possible to deprogram this parameter (programming OFF); this is not desirable since the deactivation of this safety window can lead to asystole in pacemaker-dependent patients or to the loss of biventricular pacing in non-dependent patients in case of late AV crosstalk (ventricular sensing of the atrial stimulus or atrial depolarization).
This tracing is relatively rare given that the crosstalk occurs after the safety window, which was turned on and programmed to run during the atrioventricular delay. In this particular patient, the post-sense atrial depolarization time is significantly prolonged and sensed by the ventricular channel more than 110 msec after the atrial stimulus.
Possible solution options are relatively similar to the previous tracing: 1) repositioning of the right ventricular lead; 2) reprogramming of the polarity of ventricular sensing (ineffective in this patient); 3) reprogramming the ventricular sensitivity.
In this patient, reprogramming the ventricular sensitivity to 0.6 mV eliminated the oversensing; a VF induction was used to validate the correct sensing of a ventricular arrhythmia.