Seasonal and circadian distributions of cardiac events in genotyped patients with congenital long QT syndrome.

BACKGROUND Although the incidence of ventricular tachyarrhythmias associated with structural heart disease is highest in winter and during the daytime, seasonal and circadian variations among cardiac events in patients with congenital long QT syndrome (LQTS) remain unknown. The present study aims to determine seasonal and circadian cardiac events in patients with a congenital LQTS genotype. METHODS AND RESULTS The medical records of 196 consecutive patients with symptomatic LQTS (age, 32 ± 19 years; female, n=133; LQT1, n=86; LQT2, n=95; LQT3, n=15) who were genotyped between 1979 and 2006 at 2 major Japanese institutions were retrospectively analyzed. The patients with LQT1, LQT2, and LQT3 developed 223,550 and 59 cardiac events during a mean follow-up of 26, 33, and 25 years, respectively. The numbers of cardiac events significantly peaked during the summer among those with LQT1 (P<0.001) and from summer to fall in those with LQT2 (P<0.001), but reached the nadir in winter among those with LQT3 (P=0.003). Cardiac events significantly peaked in the afternoon (12:00-17:59) and morning (06:00-11:59) among those with LQT1 (P<0.001) and LQT2 (P<0.001). CONCLUSIONS The frequency of cardiac events was specifically seasonal and circadian among patients with the 3 major genotypes of congenital LQTS.