The long QT syndrome. Prospective longitudinal study of 328 families.
- 1 September 1991
- journal article
- abstracts
- Published by Ovid Technologies (Wolters Kluwer Health) in Circulation
- Vol. 84 (3), 1136-1144
- https://doi.org/10.1161/01.cir.84.3.1136
Abstract
BACKGROUND The Long QT Syndrome (LQTS) is an infrequently occurring familial disorder in which affected individuals have electrocardiographic QT interval prolongation and a propensity to ventricular tachyarrhythmic syncope and sudden death. We prospectively investigated the clinical characteristics and the long-term course of 3,343 individuals from 328 families in which one or more members were identified as affected with LQTS (QTc greater than 0.44 sec1/2). METHODS AND RESULTS The first member of a family to be identified with LQTS, the proband, was usually brought to medical attention because of a syncopal episode during childhood or teenage years. Probands (n = 328) were younger at first contact (age 21 +/- 15 years), more likely to be female (69%), and had a higher frequency of preenrollment syncope or cardiac arrest with resuscitation (80%), congenital deafness (7%), a resting heart rate less than 60 beats/min (31%), QTc greater than or equal to 0.50 sec1/2 (52%), and a history of ventricular tachyarrhythmia (47%) than other affected (n = 688) and unaffected (n = 1,004) family members. Arrhythmogenic syncope often occurred in association with acute physical, emotional, or auditory arousal. The syncopal episodes were frequently misinterpreted as a seizure disorder. By age 12 years, 50% of the probands had experienced at least one syncopal episode or death. The rates of postenrollment syncope (one or more episodes) and probable LQTS-related death (before age 50 years) for probands (n = 235; average follow-up 54 months per patient) were 5.0% per year and 0.9% per year, respectively; these event rates were considerably higher than those observed among affected and unaffected family members. CONCLUSIONS Among 232 probands and 1,264 family members with prospective follow-up, three factors made significant independent contributions to the risk of subsequent syncope or probable LQTS-related death before age 50 years, whichever occurred first (Cox hazard ratio; 95% confidence limits): 1) QTc (1.052; 1.017, 1.088), 2) history of cardiac event (3.1; 1.3, 7.2), and 3) heart rate (1.017; 1.004, 1.031). The findings from this prospective longitudinal study highlight the clinical features, risk factors, and course of LQTS.This publication has 13 references indexed in Scilit:
- Hereditary long Q-T syndrome presenting as epilepsy: Electroencephalography laboratory diagnosisAnnals of Neurology, 1989
- Permanent cardiac pacing in patients with the long QT syndromeJournal of the American College of Cardiology, 1987
- Prolonged QT-Interval SyndromesJAMA, 1986
- The Idiopathic Long QT Syndrome: Pathogenetic Mechanisms and TherapyEuropean Heart Journal, 1985
- Idiopathic long QT syndrome: Progress and questionsAmerican Heart Journal, 1985
- Congenital Deafness with Cardiac Arrhythmias: The Jervell and Lange-Nielsen SyndromeAmerican Annals of the Deaf, 1980
- The long Q-T syndromeAmerican Heart Journal, 1975
- Nonparametric Estimation from Incomplete ObservationsJournal of the American Statistical Association, 1958
- Congenital deaf-mutism, functional heart disease with prolongation of the Q-T interval, and sudden deathAmerican Heart Journal, 1957