Occasional dropped ventricular pacing in a patient with no underlying rhythm and an Advisa® dual-chamber pacemaker.

An 86-year-old white male with complete heart block and no underlying ventricular escape rhythm was implanted with an Advisa MRI dual-chamber pacemaker. Telemetry recordings revealed occasional, isolated P waves without pacing spikes or paced QRS complexes. Decreasing the right ventricle (RV) channel sensitivity to a value of 1.2 mV or higher eliminated completely this phenomenon. The observance of an occasional dropped ventricular paced (VP) event is possible in the Advisa family of devices and occurs during the collection of reference electrogram (EGM). Specifically, turning on/off the EGM amplifiers results in a disturbance of the RV sense amplifier. The intermittent electrical disturbance occurs infrequently, but timed to a predictable interval—a multiple increment of an hour and 30 s. This specific interval increment is associated with the scheduling of the reference EGM collection. Infrequent, occasional dropped VP events are most likely to occur when collection of the reference EGM is synchronized to an atrial sense (AS) event during complete heart block, since cross-chamber blanking following an AS event is not active in the device.