Prolonged QTc, Thiazides, and Sudden Death-Reply

Abstract

In Reply.— Dr Kirkendall refers to a recent article1describing an association between the use of the combination of ketanserin with potassium-losing diuretics and an increased number of deaths as compared with the use of potassium-sparing diuretics or placebo. Since ketanserin prolonged the QTcinterval, it was postulated that ketanserin in the presence of hypokalemia caused more frequent cardiac arrhythmias, some of which could be fatal. Ketanserin, however, is not marketed in this country and, therefore, does not present a real clinical problem. Furthermore, thiazides alone do not cause a prolonged QTcinterval. Holter monitor studies in asymptomatic hypertensive patients who took rather large doses of thiazide and many of whom became hypokalemic failed to show any increase in arrhythmic activity, including ventricular tachycardia.2 Kirkendall states that ventricular tachycardia also can be induced with potassium-losing diuretics plus other drugs that prolong the QTcinterval. He