Loss of biventricular pacing due to long PR interval and P wave in the PVARP

Patient

65 years old man, implanted with a triple chamber defibrillator Protecta XT CRT-D for primary cardiomyopahty with sinus dysfunction, left bundle branch block and long PR; routine follow-up 6 months after implantation; recording of spontaneous ventricular sensed event.

Trace

Tracing

Episodes of ventricular sensed event in the device memory;

atrial sense and biventricular pacing (AS-BV) ;
probable ventricular premature beat;
atrial activity falling in the PVARP, No AV delay and absence of biventricular pacing ;
consecutive AR-VS cycles with prolonged loss of biventricular pacing ;

RV threshold test in VDI mode at 90bpm ;

ventricular capture with dissociated atrial rythm followed by a conduction from the atrium to the ventricule: AS-VS cycles with long PR interval ; interruption of the test ;
during the last stimulation of the threshold test (VP), prolongation of the PRAPV; sinus activity falling in the PVARP;
successive AR-VS cycles with a long PR interval and sinus P wave in the PVARP ;
moderate sinus pause allowing the P wave to fall outside the PVARP
recovery of biventricualr pacing;

Modification the device programming (atrial tracking rate algorithm is turned ON); the patient is discharged ;

New episodes of ventricular detection recorded by the device ;

atrial sense and biventricular pacing (AS-BV) ;
probable ventricular quadruplet ;
atrial activity falling in the PRAPV, No AV delay and absence of biventricular stimulation ; succession AR-VS cycles with prolonged loss biventricular pacing ;
intervention of the atrial tracking rate algorithm; shortening of the PRAPV ; recovery of the biventricular pacing ;

Comments

This example illustrates a relatively common cause of loss of biventricular pacing in patients with long PR. Following a loss of atrio-ventricular synchrony (ESV, pacing threshold…), a P wave falls in the PVARP, and does not launch an new AV delay. As results, spontaneous conducted ventricular events appear. The probability that the P wave falls into the PVARP and maintains the phenomenon increases with the PR duration (the longest, the more important is the risk), the sinus rate (the fastest, the higher is the risk) and the programming of some algorithms (PVARP extension after VPB, auto-threshold procedure, automatic PVARP). The programming of these algorithms should be discussed case-by-case, particularly in CRT patients with long PR (higher risk of occurrence of this type of phenomenon with a theoretically lower risk of PMT in the presence of impaired AV conduction). Programming the atrial tracking rate algorithm interrupt the repetition of these cycles. This algorithm must be systematically programmed ON.

Pacing & Defibrillation

ECG

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