P wave oversensing in a unipolar VVI pacemaker.

A 45-year-old male had a VVI pacemaker implanted 20 years ago because of complete heart block. Because of perforation of the lead the pulse generator was removed after 4 weeks and a second lead was implanted from the contralateral side. Recently, the patient presented with symptoms of lightheadedness and syncope associated with prolonged pauses in the electrocardiogram. From the ECG, the ECG interpretation channel, and intracardiac electrogram telemetry, it was concluded that the VVI pacemaker was inhibited by P waves. The most likely explanation for this phenomenon was an insulation defect in the functioning lead caused by friction with the abandoned lead at the level of the high right atrium.