Effect of intravenous ketanserin on the human action potential duration at fixed heart rate.

In this study any changes in action potential duration or Q-T interval due to acute doses of ketanserin were monitored. The effect of a bolus dose (10 or 20 mg) followed by an infusion (10 or 20 mg over 20 minutes) of ketanserin on the Q-T interval and action potential duration was studied in six patients undergoing routine cardiac catheterization. Action potential duration was measured with a silver-silver chloride electrode catheter while heart rate was kept constant by atrial pacing and reflex effects avoided by beta-adrenergic blockade. There were some prolongations of the action potential duration but they were not in excess of 40 msec and did not reach statistical significance (control 263 +/- 46.0 msec; bolus 269 +/- 52.1 msec; infusion 262 +/- 53.6 msec; nor were there any significant changes in Q-T interval. Thus acute intravenous doses of ketanserin, in the absence of hypokalaemia or other Q-T interval-prolonging drugs, have no consistent effect on Q-T interval or action potential duration; prolongation of the action potential, when it occurs, is small.