Fig. 3.
Example of undersensing that caused excess pacing in the operating room. (A) The right ventricular electrogram and the channel markers are shown while the lead sensitivity was set to 2.5 mV. Shown on the electrogram are six ventricular depolarizations that are not sensed by the device (down-pointing arrows). In addition, ventricular-paced beats are observed, often shortly after unsensed ventricular depolarizations including one R-on-T paced beat (large, up-pointing arrow). (B) The right ventricular electrogram is shown after the lead was programmed to be more sensitive (threshold set to 1.5 mV). All ventricular depolarizations are now detected, and no unnecessary ventricular pacing is present. VP = ventricular pacing; VS = ventricular sensing.