Evaluation of Cases with QT Prolongation and "Torsade de Pointes"

Amiodarone is a clas III antiarrhythmic agent that is used in treatment of both supraventricular and life-threatening ventricular arrhythmias in adult and pediatric population. Although lengthening of QT interval is seen frequently during the long term use of amiodarone, it rarely causes polymorphic ventricular tachycardia (PVT) called "torsade de pointes" (TdP) episodes. In this study, 13 patients (6 female, 7 male, mean age:57±17.2 yrs) with significant QT prolongation after amiodarone due to ventricular tachycardia in our clinics were presented. Underlying disease was ischemic cardiomyopathy in 8 patients, dilated cardiomyopathy in 3 patients, however, in 2 patients no etiologic cause could be found. The earliest QT prolongation occurred in 30th and the latest in 7th day. While the shortest QT interval was 480 msec, the longest was 720 msec and the mean QT interval was calculated as 589.2±60.3 msec, the shortest QTc was 519 msec, the longest 682 msec and mean QTc was 590.2±45.3 msec. Meanwhile, there was hypokalemia in two of the patients. A spontaneous TdP episode occurred in the patient with hypokalemia due to significant QT prolongation in the 4th day of treatment and this patient died. As a result, although rare, amiodarone can cause QT prolongation and associated TdP episodes. This risk increases especially with electrolyte imbalances like hypokalemia, hypomagnesemia and hypocalcemia. For this reason, close ECG monitorization and follow for electrolyte imbalances should be done in the patients who will be treated with high dose amiodarone either orally or intravenously. (Türk Kardiyol Dern Arş 2004; 32: 145-151)