Berul C I, Sweeten T L, Dubin A M, Shah M J, Vetter V L
Division of Cardiology, Children's Hospital of Philadelphia, Pennsylvania 19104.
Am J Cardiol. 1994 Dec 15;74(12):1254-7. doi: 10.1016/0002-9149(94)90558-4.
A prolonged rate-corrected QT interval (QTc) may be associated with an increased risk of developing ventricular arrhythmias and sudden death, particularly in patients with the hereditary long QT syndrome (LQTS), myocardial ischemia, or antiarrhythmic medication toxicity. It is known that there are some patients with LQTS who sometimes have a borderline or normal QTc (< or = 0.45 second). Although the QTc has been the standard measurement of ventricular repolarization, it includes both depolarization and repolarization and may not always be a sensitive indicator of the type of repolarization abnormalities seen in LQTS. Intraventricular conduction abnormalities complicate evaluation of the QTc interval. The rate-corrected JT interval (JTc) is a more accurate measurement of ventricular repolarization, and therefore may be a more sensitive means of assessing abnormalities. The QTc on a resting electrocardiogram was determined in 40 patients with LQTS and in 31 patients with right bundle branch block after tetralogy of Fallot repair. These were compared with 1,000 age-matched control subjects. The right bundle branch block group had normal JT and JTc measurements, despite having prolonged QT and QTc intervals compared with controls. The JTc identified 85% of patients affected with LQTS compared with only 58% identified using only the QTc as a marker for the syndrome. The JTc is a more specific measurement of ventricular repolarization than the QTc by eliminating QRS duration variability. It appears to be a more sensitive predictor of repolarization abnormalities, and may be helpful in identifying patients with LQTS who have borderline or normal QTc measurements on resting electrocardiograms.
校正心率后的QT间期（QTc）延长可能与室性心律失常及猝死风险增加有关，尤其是在患有遗传性长QT综合征（LQTS）、心肌缺血或抗心律失常药物中毒的患者中。已知有些LQTS患者有时QTc处于临界值或正常范围（≤0.45秒）。尽管QTc一直是心室复极的标准测量指标，但它包含了去极化和复极化过程，对于LQTS中所见的复极异常类型可能并不总是一个敏感指标。心室内传导异常会使QTc间期的评估变得复杂。校正心率后的JT间期（JTc）是心室复极更准确的测量指标，因此可能是评估异常情况更敏感的方法。对40例LQTS患者及31例法洛四联症修复术后发生右束支传导阻滞的患者进行了静息心电图QTc测定，并与1000名年龄匹配的对照者进行比较。右束支传导阻滞组的JT和JTc测量值正常，尽管与对照组相比其QT和QTc间期延长。与仅将QTc作为该综合征标志物相比，JTc能识别出85%的LQTS患者，而仅用QTc识别出的患者为58%。通过消除QRS波时限的变异性，JTc比QTc是更特异的心室复极测量指标。它似乎是复极异常更敏感的预测指标，可能有助于识别静息心电图QTc测量处于临界值或正常范围的LQTS患者。
