Complications of defibrillation with permanent pacemaker in situ.

A permanent demand pacing generator was implanted in the right deltopectoral fossa with unipolar transvenous lead advanced to the right ventricle. Implant and subsequent pacing parameters were normal. Five days later an emergency DC cardioversion was performed with one paddle 2 inches from the generator. Cardioversion was followed by failure of QRS-sensing and, at immediate explant, rise in stimulation threshold. The pulse generator showed end-of-life characteristics. The patient died 4 days following replacement of the generator and lead. At autopsy, right ventricular infarction was found, presumably relating to current discharge along the lead. Pacemaker analysis showed damage to the protection zener diode and oscillator integrated circuit of the generator during cardioversion.