EVALUATION OF AUTONOMIC NERVOUS ACTIVITY IN PATIENTS WITH CONGENITAL LONG QT SYNDROME BY AN ANALYSIS OF RR VARIABILITY

Congenital long QT syndrome (LQTS) is a rare hereditary disease charac terized by a prolonged QT interval and lethal ventricular tachycardia (Torsades de Pointes: TdP). The pathogenesis of LQTS and the induction of TdP have been thought to be closely related to autonomic nervous a bnormalities. We examined autonomic activity in 13 LQTS patients by an alyzing heart rate variability from 24 h Holter ambulatory electrocard iographic recordings without medications. In a frequency-analysis of R R variability, we calculated the power in the low-frequency domain (LF ) and the high-frequency domain (HF) over 24 h. The ratio of LF to HF (an index of sympathetic nervous activity) was lower in LQTS patients than in controls, whereas HF (an index of parasympathetic nervous acti vity) was higher. Moreover, LQTS patients with TdP had lower abnormal sympathetic nervous activity than those without TdP. The index of auto nomic nervous activity obtained using this method could be useful for evaluating the severity in LQTS.