Viitasalo M, Rovamo L, Toivonen L, Pesonen E, Heikkilä J
Department of Medicine, Helsinki University Central Hospital, Finland.
Eur Heart J. 1996 Nov;17(11):1723-8. doi: 10.1093/oxfordjournals.eurheartj.a014757.
The dynamics and homogeneity of the QT interval have been used as indicators of susceptibility to ventricular arrhythmias. We determined the relationship between QT intervals and heart rate during exercise testing and subsequent recovery in 18 healthy children. The QT intervals were measured to the apex (early QT), to the end (total QT), and from the apex to the end of the T wave (late QT) (inhomogeneity of repolarization) at heart rates from 60 by steps of 10 to 180 beats.min-1. Group mean total QT and early QT exhibited better linear correlations with heart rate (r 0.998 and 0.999) than with cardiac cycle length (r 0.954 and 0.959). The slope relating total QT to heart rate was -1.30 during exercise and -1.42 during recovery (P < 0.05). The corresponding slopes relating early QT to heart rate were -1.11 and -1.30 (P < 0.05). Late QT, as a proportion of total QT, increased at high heart rates. Rate correction using Bazett's method gave abnormal total QT values (> 440 ms) in 12 children (67%) whereas linear correction gave values below 440 ms only. In conclusion, the relationship between QT and heart rate is linear and differs during exercise and recovery. Inhomogeneity of repolarization increases at high heart rates. Linear correction of total QT and early QT intervals improves the evaluation of repolarization duration in exercise testing in children.
QT间期的动态变化和均匀性已被用作心室心律失常易感性的指标。我们测定了18名健康儿童在运动试验及随后恢复过程中QT间期与心率之间的关系。在心率从60次/分钟以10次/分钟的步长递增至180次/分钟时，测量QT间期至T波顶点（早期QT）、至T波终点（总QT）以及从T波顶点至终点（晚期QT）（复极不均匀性）。与心动周期长度（r分别为0.954和0.959）相比，组平均总QT和早期QT与心率的线性相关性更好（r分别为0.998和0.999）。运动期间总QT与心率的斜率为-1.30，恢复期间为-1.42（P<0.05）。早期QT与心率的相应斜率分别为-1.11和-1.30（P<0.05）。晚期QT占总QT的比例在高心率时增加。使用巴泽特方法进行心率校正时，12名儿童（67%）的总QT值异常（>440毫秒），而线性校正时仅得到低于440毫秒的值。总之，QT与心率之间的关系是线性的，且在运动和恢复过程中有所不同。复极不均匀性在高心率时增加。对总QT和早期QT间期进行线性校正可改善儿童运动试验中复极持续时间的评估。
