Asthma and the risk of cardiac events in the long QT syndrome

While acquiring data for the International Long QT Syndrome Registry, we no ticed that a number of patients referred for long QT syndrome (LQTS) were a ffected by asthma. The effect of asthma comorbidity on clinical course of L QTS has nat been studied, This study aimed to evaluate the prevalence of as thma in patients with LQTS, determine the influence of asthma comorbidity o n outcome of LQTS patients, and to investigate the confounding effects of b eta mimetics and beta blockers on the occurrence of cardiac events in asthm atic patients. The influence of asthma on risk of cardiac events (syncope, aborted cardiac arrest, or LQTS death) was evaluated after accounting for a ge, gender, QTc, and RR interval duration, beta-blocker and beta-mimetic us e. Asthma was identified in 226 (5.2%) of 4,310 studied LQTS family members , Longer QTc duration was associated with higher incidence of asthma (p <0. 001). Asthma was independently associated with significantly increased risk of cardiac events in affected LQTS patients (hazard ratio 1.32; p = 0.048) and in borderline-affected family members (hazard ratio 2.08; p = 0.004) a fter adjustment for QTc, RR interval, and gender, An increased risk of card iac events in asthmatic patients observed before beta-blocker therapy was r educed after initiation of treatment with beta blockers. In conclusion, the occurrence of asthma in LQTS patients increases with QTc duration. Asthma comorbidity in LQTS patients is associated with an increased risk of cardia c events. The asthma-associated increase in the risk of LQTS-related cardia c events is diminished after initiation of beta-blocker therapy, suggesting a possible role of beta-receptor modulation under lying asthma-LQTS associ ation. (C) 1999 by Excerpta Medica, Inc.