Long QT syndrome caused by N-acetyl procainamide in a patient on hemodialysis

摘要

A 65-year-old male on hemodialysis three times a week due to end-stage renal failure underwent cardiac surgery one year previously, and complained of breathlessness on exertion after surgery. Echocardiograms evidenced a significant obstruction in the left ventricular outflow with intraventricular pressure gradient of 62 mmHg, and the patient was started on beta-blocker. After a maximal dose of carvedilol was given, a class 1A antiarrhythmic drug of Na channel blocker, procainamide, was added because of insufficient relief of symptoms. Electrocardiogram (ECG) showed prolonged QT intervals (523 ms) on a regular visit one month after the administration of procainamide, and the dose of procainamide was decreased. On the next day, he was brought to our hospital due to cardiac pulmonary arrest. Initial rhythm was ventricular fibrillation and the corrected QT intervals (QTc) were prolonged (531 ms). Blood examination revealed that N-acetyl procainamide (NAPA), metabolite of procainamide, was significantly higher than the recommended threshold. NAPA was identified as the cause of prolonged QTc and procainamide was stopped. NAPA decreased under the recommended threshold on the seventh day and the QT intervals were normalized. This case report outlines the first case of long QT syndrome caused by NAPA in a hemodialysis patient.<>Learning objective: Administration of procainamide could be dangerous even in patients undergoing hemodialysis whose serum procainamide level is within normal limits. We should pay careful attention to it and must not forget to measure the concentrations of procainamide and NAPA. The measurement of QT intervals could help to avoid a fatal side effect.>