Case History
A 92-year-old man was admitted to our hospital for pacemaker generator exchange. He was small, with 150 cm in height and 43 kg in weight. A dual-chamber pacemaker (Identity™, St. Jude Medical Japan, Tokyo, Japan) was implanted for sick sinus syndrome 12 years ago, and a daily dose of 200 mg bepridil was started for associated paroxysmal atrial fibrillation by a general cardiologist in charge at that time. The bepridil prescription had been continued by his family physician. He visited the pacemaker clinic once every 6 months regularly and had not experienced any pacemaker-related problems. After 12 years of pacemaker usage, because the battery of the pacemaker had reached its elective replacement indicator, a scheduled pacemaker generator exchange was planned. The electrocardiogram at the pacemaker clinic showed atrial and ventricular pacing with corrected QT interval of 578 ms, JT interval of 428 ms, and QT dispersion of 109 ms (Fig. 1).
During the pacemaker generator exchange operation, QT prolongation occurred just after pacemaker reprograming to lower the heart rate setting (Fig. 2A). Subsequently, atrial fibrillation and TdP occurred (Fig. 2B). Fortunately, TdP was successfully terminated by 150 J defibrillation without any serious sequelae. The pacemaker generator exchange was completed using temporary backup pacing, which was immediately established after successful resuscitation. The serum potassium concentration was normal at 4.6 mEq/L. Genetic screening showed no mutation in KCNQ1 , KCNH2 , SCN5A ,KCNE1 , or HCN4 and a missense mutation in L897T,which was considered benign or likely benign. The plasma concentration of bepridil was high at 1409 ng/mL. We concluded that TdP was caused by bepridil intoxication, and bepridil prescription was stopped. After cessation of bepridil prescription, the patient had been free from TdP for 45 months. Although the persistent atrial fibrillation became permanent atrial fibrillation, the patient had not experienced other adverse events since then.