Triggers for cardiac events in long QT syndrome are related to genotype

In a study of 670 patients with long QT syndrome and known genotype, all symptomatic (syncope, aborted cardiac arrest, or sudden death), the occurrence of a lethal cardiac event (n = 110) provoked by a specific trigger (exercise, emotion, and sleep/rest without arousal) differed according to genotype. LQT1 patients experienced most of their events (90%) during exercise or emotion. These percentages were almost reversed among LQT2 and LQT3 patients who had most of their events during rest or sleep (63 and 80%, respectively); by contrast, they were at almost no risk of major events during exercise (arrows), which is explained by their having a normal I_Ks current.