Swan H, Toivonen L, Viitasalo M
Department of Medicine, Helsinki University Central Hospital, Finland.
Eur Heart J. 1998 Mar;19(3):508-13. doi: 10.1053/euhj.1997.0764.
To improve the diagnostic criteria of the congenital long QT syndrome in borderline cases we examined rate adaptation of ventricular repolarization phases during exercise and subsequent recovery in children with the long QT syndrome and controls.
Nineteen children with definite long QT syndrome and 19 healthy controls underwent exercise testing. QT intervals were measured to the apex (early QT), to the end (total QT) and from apex to the end of the T wave (late QT) at heart rates from 90 by steps of 10 to 150 beats, min-1.
In 11/19 long QT syndrome patients (61%) and 2/19 controls (12%) the total QT lengthened during the recovery phase compared with exercise (P = 0.005) at the lowest comparable heart rate. No difference was found between the groups during exercise. The sensitivity of rate adaptation of repolarization intervals was analysed by calculating linear regression slopes relating the QT intervals to the heart rates. During recovery, slopes relating the total QT to heart rate were steeper in long QT syndrome patients than those in controls (-2.50 +/- 0.82 vs -1.79 +/- 0.47, P = 0.003). Total QT/heart rate slopes differed between exercise and recovery phases in the long QT syndrome group only (-1.77 +/- 0.71 vs 2.50 +/- 0.82, P = 0.009). In long QT syndrome patients, the difference in total QT/heart rate slopes was mainly because the late QT/heart rate slopes indicating inhomogeneity of repolarization were steeper during recovery (-1.27 +/- 0.74) than during exercise (-0.46 +/- 0.29, P < 0.0001).
After exercise in long QT syndrome children the QT interval lengthens abnormally and inhomogeneity of repolarization increases. Evaluation of the QT interval, and especially its late portion after exercise, may help in establishing the diagnosis of long QT syndrome.
为了改进临界病例中先天性长QT综合征的诊断标准，我们检测了长QT综合征患儿及对照组在运动及随后恢复过程中心室复极期的心率适应性。
19例确诊为长QT综合征的患儿和19名健康对照者接受运动试验。在心率从90次/分钟逐步递增至150次/分钟的过程中，测量QT间期至顶点（早期QT）、至结束（总QT）以及从顶点至T波结束（晚期QT）。
在最低可比心率时，11/19例（61%）长QT综合征患者和2/19例（12%）对照者的总QT在恢复阶段较运动时延长（P = 0.005）。运动期间两组间未发现差异。通过计算QT间期与心率的线性回归斜率来分析复极间期的心率适应性敏感性。在恢复过程中，长QT综合征患者总QT与心率的斜率比对照组更陡（-2.50±0.82对-1.79±0.47，P = 0.003）。仅在长QT综合征组中，运动期和恢复期的总QT/心率斜率不同（-1.77±0.71对-2.50±0.82，P = 0.009）。在长QT综合征患者中，总QT/心率斜率的差异主要是由于恢复期间表明复极不均一性的晚期QT/心率斜率比运动时更陡（-1.27±0.74对-0.46±0.29，P < 0.0001）。
长QT综合征患儿运动后QT间期异常延长且复极不均一性增加。评估QT间期，尤其是运动后的晚期部分，可能有助于长QT综合征的诊断。
