Johnson J N, Ackerman M J
Department of Pediatrics/Division of Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Br J Sports Med. 2009 Sep;43(9):657-62. doi: 10.1136/bjsm.2008.054734.
Congenital long QT syndrome (LQTS) affects an estimated 1 in 2500 people and typically presents with syncope, seizures or sudden death. Whereas someone exhibiting marked prolongation of the QT interval with QTc exceeding 500 ms who was just externally defibrillated from torsades de pointes while swimming poses negligible diagnostic challenge as to the unequivocal probability of LQTS, the certainty is considerably less for the otherwise asymptomatic person who happens to host a QTc value coined "borderline" (QTc > or = 440 ms). Although a normal QT interval imparts a much lower risk of life-threatening events, it does not preclude a patient from nevertheless harbouring a potentially lethal LQTS-causing genetic mutation. Indeed, genetic testing exerts significant diagnostic, prognostic and therapeutic implications. However, the 12-lead ECG remains the universal initial diagnostic test in the evaluation of LQTS and is subject to miscalculation, misinterpretation and mishandling. This review discusses the components of accurate QTc measurement and diagnosis, re-examines what is known about factors affecting QT interval measurement, and clarifies current recommendations regarding diagnosis of so-called "borderline" QT interval prolongation. The current guideline recommendations for the athlete with LQTS are also summarised.
先天性长QT综合征（LQTS）估计影响着每2500人中的1人，通常表现为晕厥、癫痫发作或猝死。对于一名QT间期显著延长且QTc超过500毫秒的人，他在游泳时刚从尖端扭转型室速中接受体外除颤，LQTS的明确可能性对其诊断几乎没有挑战；而对于一名偶然拥有被称为“临界”（QTc≥440毫秒）QTc值的无症状者，其确诊的把握性则要小得多。虽然正常的QT间期会使危及生命事件的风险大大降低，但这并不能排除患者携带潜在致命的导致LQTS的基因突变。事实上，基因检测具有重要的诊断、预后和治疗意义。然而，12导联心电图仍然是评估LQTS的通用初始诊断测试，并且容易出现计算错误、解读错误和处理不当的情况。本综述讨论了准确QTc测量和诊断的组成部分，重新审视了已知的影响QT间期测量的因素，并阐明了关于所谓“临界”QT间期延长诊断的当前建议。还总结了目前针对LQTS运动员的指南建议。
