An 81-year-old asymptomatic woman underwent implantation of an Adapta dual chamber pacemaker for management of atrial disease, which evolved toward well controlled chronic AF; programming in VVIR mode at 60-120 bpm; she was seen on routine follow-up.
The first channel is lead III of the surface ECG with the markers superimposed, the second shows the ventricular EGM and the third is lead II with the intervals superimposed;
This tracing shows ventricular undersensing due to faulty programming. The bipolar ventricular EGM measured 3.8 mV, and the device was programmed with a 5-mV sensitivity. In absence of proper sensing, the pacemaker operates as in VOO mode, with no inhibition by the spontaneous ventricular events, as they are not sensed.
In these circumstances 1) a large amount of energy is expended unnecessarily (ventricular pacing without capture or with useless and dangerous capture) 2) it creates a risk of proarrhythmia when the ventricle is paced during the vulnerable period. Programming of an appropriate sensitivity rectified the problem.
