The long QT syndrome: Prospective longitudinal study of 328 families

Arthur J. Moss, Peter J. Schwartz, Richard S. Crampton, Dan Tzivoni, Emanuela H. Locati, Jean MacCluer, W. Jackson Hall, Lowell Weitkamp, G. Michael Vincent, Arthur Garson, Jennifer L. Robinson, Jesaia Benhorin, Sungsub Choi

Research output: Contribution to journalArticlepeer-review


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>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≥0.50 sec1/2 (52%), and a history of ventricular tachyarrhythmia (47%) than other affected (R=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 0.0% 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.

Original languageEnglish
Pages (from-to)1136-1144
Number of pages9
Issue number3
Publication statusPublished - Sep 1991


  • Delayed repolarization
  • Stellectomy
  • Sudden cardiac death
  • Syncope
  • Ventricular arrhythmias

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine


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