QT prolongation and torsade de pointes ventricular tachycardia produced by Ketanserin.

A 65-year-old man with arterial hypertension received oral treatment with Ketanserin, a new drug, during a period of five months. He developed marked QT interval prolongation and have several Stokes-Adams attacks. A Holter recording obtained during one of these episodes showed torsade de pointes ventricular tachycardia. The arrhythmias occurred during maximum QT interval prolongation. The correlation between Ketanserin and QT interval prolongation was evaluated by using several Holter studies during administration and withdrawal of the drug. The effect of Ketanserin on the QTc interval was analyzed retrospectively in six patients who had been taking the drug orally. Following a period of four to eight months, the QTc interval was prolonged by the drug (5 to 31%, mean 17%) in five patients. We conclude that torsade de pointes is a potential hazard of long-term treatment with Ketanserin.