Rudehill A, Sundqvist K, Sylvén C
Clin Physiol. 1986 Feb;6(1):23-37. doi: 10.1111/j.1475-097x.1986.tb00140.x.
To study the properties of QT and QT-peak intervals, ECGs were compared between 56 consecutive patients who were suffering from subarachnoid haemorrhage (SAH) and 50 reference subjects. The routine QTc interval was compared to the mean QTc from all of the 12 leads with identifiable U waves and to the mean QT-peakc. The interval between peak and end of T(Tp-Te) was subsequently calculated. In the reference group the mean QT-peak correlated with the mean QT (r = 0.925). The rate-dependence of the mean QT-peak was not different from that of the mean QT and showed the same correlation (r = -0.607 and -0.630, respectively). No rate-dependence for the Tp-Te interval could be demonstrated. Following SAH, ECG abnormalities were most pronounced after 8-9 days, and increased with age and the degree of cerebral dysfunction. Two patient groups, where the mean QTc of each particular patient was either below (n = 27) or above (n = 29) the reference limit, were analysed. For the group without an abnormally prolonged mean QTc, the average of the individual mean QTc was significantly longer than in the reference group. Both groups had longer mean QT-peakc intervals than the reference group. About 70% of the patients with an abnormally prolonged mean QTc also had a prolonged mean QT-peakc interval, while the rest had a prolonged Tp-Tc interval; simultaneous prolongation of these two intervals also occurred. Prolongation of the Tp-Te interval did not occur in the group without an abnormally prolonged mean QTc. Routine QTc and mean QT-peakc had sensitivities of 96% and 67% respectively, specificities of 76% and 96% and predictive values of 81% and 95%. In conclusion, the routine QTc measurements, without reference to an identified U wave, may result in falsely prolonged estimates of cardiac repolarization time. In this respect the mean QT-peakc may provide additional information. In the majority of patients the prolonged mean QTc was dependent on a disturbed rate-dependent function (prolonged mean QT-peakc) while some patients had an increased asymmetry of the repolarization process within the myocardium (prolonged Tp-Tc).
为研究QT及QT峰间期的特性，对56例连续性蛛网膜下腔出血（SAH）患者和50例对照者的心电图进行了比较。将常规QTc间期与12个可识别U波导联的平均QTc以及平均QT峰进行比较。随后计算T波峰与终末之间的间期（Tp-Te）。在对照组中，平均QT峰与平均QT相关（r = 0.925）。平均QT峰的心率依赖性与平均QT无差异，且显示出相同的相关性（分别为r = -0.607和-0.630）。未证实Tp-Te间期存在心率依赖性。SAH后，心电图异常在8 - 9天后最为明显，并随年龄和脑功能障碍程度增加。分析了两个患者组，每组中各患者的平均QTc要么低于（n = 27）要么高于（n = 29）参考限值。对于平均QTc未异常延长的组，个体平均QTc的平均值显著长于对照组。两组的平均QT峰间期均长于对照组。平均QTc异常延长的患者中约70%的平均QT峰间期也延长，其余患者的Tp-Tc间期延长；这两个间期也会同时延长。平均QTc未异常延长的组未出现Tp-Te间期延长。常规QTc和平均QT峰的敏感性分别为96%和67%，特异性分别为76%和96%，预测值分别为81%和95%。总之，在未参考明确U波的情况下，常规QTc测量可能会导致心脏复极时间的估计值假性延长。在这方面，平均QT峰可能提供额外信息。在大多数患者中，平均QTc延长取决于紊乱的心率依赖性功能（平均QT峰延长），而一些患者心肌内复极过程的不对称性增加（Tp-Tc延长）。
