Clinical and genetic variables associated with acute arousal and nonarousal-related cardiac events among subjects with the long QT syndrome

In patients with the long QT syndrome (LQTS), the occurrence of cardiac eve nts (syncope or cardiac arrest) is frequently associated with acute arousal caused by exercise, swimming, emotion, or noise. However, cardiac events m ay also occur during sleep or with ordinary daily activities. The purpose o f this study was to determine whether there are differential clinical, elec trocardiographic, and genetic features among LQTS patients who experienced cardiac events with and without acute arousal. We identified 1,325 patients with cardiac events from the International LQTS Registry. Based on the pre cipitating conditions of the first event, 427 patients were classified as a rousal, 345 as nonarousal, and the remaining 553 were unknown (not classifi able). Gene linkage was known in 78 of the 772 patients with classifiable f irst events. The age at first cardiac event was significantly younger in th e arousal than the non-arousal group (11.7 vs 15.5 years, respectively; p < 0.001). The arousal-type patients had a higher rate of subsequent cardiac e vents during follow-up after the index event than the nonarousal-type patie nts (p = 0.02). Arousal-related cardiac events occurred in 85% of LQT1, 67% of LQT2, and 33% of LQT3 patients (p = 0.008). This study provides evidenc e that the genotype is on important determinant of the LQTS phenotype in te rms of arousal and nonarousal-related cardiac events. (C) 2000 by Excerpta Medico, Inc.