Under-sensing by a temporary pacemaker after cardiac surgery and ventricular fibrillation

An 80-year-old man with a 6-month-history of shortness of breath on minimal exertion and fatigue was admitted to our unit for a planned operation to replace his stenotic aortic valve. The surgery was uneventful and a temporary ventricular epicardial pacing lead was placed on the free wall of the right ventricle. The patient remained haemodynamically stable in sinus rhythm post-surgery and was extubated 8 h later. The following day he was transferred from intensive care to our high dependency unit with the temporary epicardial pacemaker in VVI mode: stimulation amplitude 10 V, sensitivity 1 mV, and back-up pacing rate of 44 beats per min. A pacing check at that time showed no problems.