Risk for Severe Cardiac Events in Adolescents with Long-QT Syndrome

Risk for Severe Cardiac Events in Adolescents with Long-QT Syndrome

Higher risk was associated with a history of syncope, QTc prolongation, and male sex.

Most previous studies have evaluated the effect of risk factors on syncope among children with long-QT syndrome (LQTS). In an industry-supported study, investigators followed 2772 adolescents with clinically suspected LQTS who were alive at age 10 through age 20 years to determine risk factors for aborted cardiac arrest and sudden cardiac death. The mean QTc for the study group was 494 ms. Before age 10, 10% of the patients received ß-blockers, and 16% had syncope.

During follow-up, aborted cardiac arrest occurred in 81 adolescents, and sudden cardiac death occurred in 45. A QTc greater than 530 ms significantly increased the risk for a serious cardiac event compared to a QTc less than 530 ms (hazard ratio, 2.3). Compared with no syncope in the past 10 years, a history of syncope was associated with increased risk. A single recent syncopal episode (within 2 years) had an HR of 11.7; two or more recent syncopes had an HR of 18.1. One syncope in the past 2 to 10 years (with no recent events) had an HR of 2.7; two or more syncopal episodes in this same timeframe had an HR of 5.8. Boys aged 10 to 12 years had a higher risk for serious cardiac events than age-matched girls (HR, 4.0). However, sex did not influence risk among 13- to 20-year-olds. Among individuals with recent syncope, treatment with ß-blockers significantly reduced the risk for a serious cardiac event by 64%. Family history of a cardiac event, LQTS genotype, and use of an implantable pacemaker were not independently associated with a serious cardiac event.

Comment: A history of syncope, the length of QTc prolongation, and patient sex were strong predictors for serious cardiac events. The authors emphasize that these risk factors can be assessed in the office. Use of ß-blockers or implantable pacemakers should be considered for high-risk patients.

— F. Bruder Stapleton, MD

Published in Journal Watch Pediatrics and Adolescent Medicine November 8, 2006