[Failure of the pacemaker in electric cardioversion of atrial fibrillation]

A 72-year-old man with an AAI-rate-responsive pacemaker (Siemens-Elema Sensolog III; unipolar pacing electrode) was admitted for cardioversion of atrial fibrillation. Electrical defibrillation was followed by severe nodal bradycardia and pacemaker malfunction characterized by loss of atrial capture. The pacemaker failure was due to an acute rise in the stimulation threshold, possibly secondary to current-induced tissue damage at the electrode-endomyocardial interface. It is recommended that a pacemaker is reprogrammed to maximum pulse voltage amplitude prior to elective DC-cardioversion and that serial measurements of the myocardial stimulation threshold are performed after defibrillation. Other factors essential for the management of the pacemaker patient who requires electrical defibrillation are outlined.