Priori S G, Napolitano C, Diehl L, Schwartz P J
Istituto di Clinica Medica Generale e Terapia Medica, Università di Milano, Italy.
Circulation. 1994 Apr;89(4):1681-9. doi: 10.1161/01.cir.89.4.1681.
QT interval dispersion, measured as interlead variability of QT, is a marker of dispersion of ventricular repolarization and, hence, of cardiac electrical instability. We tested the hypothesis that dispersion of ventricular repolarization may be differently affected by interventions destined to provide complete or incomplete protection against malignant arrhythmias in patients with long QT syndrome (LQTS). Twenty-eight patients affected by the Romano Ward form of LQTS entered the study and were divided into three groups: LQTS patients before institution of therapy, patients who did respond to beta-blocker therapy, and patients who continued to have syncope and cardiac arrest despite beta-blockade and who underwent left cardiac sympathetic denervation. A group of 15 healthy volunteers served as control subjects.
Dispersion of QT and QTc were calculated using two indexes: the difference between the longest and the shortest value measured in each of the 12 ECG leads (QTmax-QTmin, QTcmax-QTcmin) and the relative dispersion of QT and QTc (standard deviation of QT/QT average x100, standard deviation of QTc/QTc average x100). Both indexes of dispersion of repolarization were higher in the LQTS patients than in control subjects; also, patients not responding to beta-blockers had a significantly higher dispersion of repolarization than responders. A cutoff value of 100 milliseconds for QTmax-QTmin had an 80% sensitivity and 82% specificity in discriminating between responders and nonresponders. A cutoff value of 6 for QT relative dispersion yielded similar results. The LQTS patients who did not respond to beta-blockade underwent left cardiac sympathetic denervation and thereafter remained asymptomatic (mean follow-up, 5 +/- 4 years). In this group, dispersion of repolarization was significantly reduced by the surgical denervation to values similar to that of the responders to beta-blockade.
These data indicate that QT dispersion is a useful clinical tool to predict efficacy of antiadrenergic therapy in LQTS patients.
QT间期离散度，通过导联间QT的变异性来测量，是心室复极离散度的一个指标，因此也是心脏电不稳定的指标。我们检验了这样一个假设，即对于长QT综合征（LQTS）患者，旨在提供完全或不完全保护以防恶性心律失常的干预措施，可能对心室复极离散度产生不同影响。28例患有Romano Ward型LQTS的患者进入该研究，并被分为三组：治疗开始前的LQTS患者、对β受体阻滞剂治疗有反应的患者，以及尽管接受了β受体阻滞剂治疗仍有晕厥和心脏骤停并接受了左心交感神经去神经支配的患者。15名健康志愿者作为对照组。
使用两个指标计算QT和QTc的离散度：在12个心电图导联中测量的最长值与最短值之间的差值（QTmax - QTmin，QTcmax - QTcmin）以及QT和QTc的相对离散度（QT标准差/QT平均值×100，QTc标准差/QTc平均值×100）。复极离散度的两个指标在LQTS患者中均高于对照组；此外，对β受体阻滞剂无反应的患者的复极离散度显著高于有反应的患者。QTmax - QTmin的截断值为100毫秒时，在区分有反应者和无反应者方面具有80%的敏感性和82%的特异性。QT相对离散度的截断值为6时产生了类似的结果。对β受体阻滞剂无反应的LQTS患者接受了左心交感神经去神经支配，此后一直无症状（平均随访5±4年）。在该组中，手术去神经支配使复极离散度显著降低至与β受体阻滞剂有反应者相似的值。
这些数据表明，QT离散度是预测LQTS患者抗肾上腺素能治疗疗效的有用临床工具。
