Effects of the chromanol 293B, a selective blocker of the slow, component of the delayed rectifier K+ current, on repolarization in human and guinea pig ventricular myocytes

293B is a selective IKs blocker, and the frequency dependence of APD prolongation caused by this IKs blocker is different from that caused by IKr blockade: 293B may be an interesting tool to study the physiologic role of IKs and the antiarrhythmic potential of IKs blockade.