Koponen Mikael, Marjamaa Annukka, Väänänen Heikki, Tuiskula Annukka M, Kontula Kimmo, Swan Heikki, Viitasalo Matti
Heart and Lung Center, Helsinki University Hospital, Helsinki, Finland.
Heart and Lung Center, Helsinki University Hospital, Helsinki, Finland.
Heart Rhythm. 2022 Sep;19(9):1491-1498. doi: 10.1016/j.hrthm.2022.04.028. Epub 2022 May 4.
Long QT syndrome (LQTS) is an inherited arrhythmia disorder characterized by ventricular repolarization abnormalities and a risk of sudden cardiac death. The electrophysiological components generating the high risk of arrhythmias in LQTS are prolonged repolarization, increased dispersion of repolarization, and early afterdepolarizations, which are clinically estimated as QT interval, T-wave peak to T-wave end (TPE) interval, and T2/T1-wave amplitude ratio, respectively. In experimental LQTS type 2 (LQT2) models, β-blockers decrease dispersion of repolarization and prevent early afterdepolarizations. In clinical studies in patients with LQT2 , β-blockers are more effective against exercise-induced than arousal-induced cardiac events.
The aim of the study was to investigate the effects of β-blocker therapy on repolarization properties in LQT2.
QT and TPE intervals and maximal T2/T1-wave amplitude ratios recorded by 24-hour electrocardiograms before and during β-blocker therapy were evaluated in 25 patients with LQT2.
β-Blocker therapy decreased the maximal T2/T1-wave amplitude ratio from 2.9 ± 1.1 to 1.8 ± 0.7 (P < .001), but did not change the pause-induced T2/T1-wave amplitude ratio. Under medication, abrupt maximal TPE intervals were shorter at heart rates of ≥75 beats/min and maximal QT intervals were shorter at a heart rate of 100 beats/min.
β-Blockers stabilize ventricular repolarization in LQT2 by reducing electrocardiographic early afterdepolarizations and by reducing abrupt prolongation of electrocardiographic dispersion of repolarization and ventricular repolarization duration at elevated heart rates. The effect of β-blockers on pause-induced electrocardiographic early afterdepolarizations is weak. The findings provide electrocardiographic explanation for the protective effects of β-blockers against exercise-induced cardiac events in LQT2.
长QT综合征（LQTS）是一种遗传性心律失常疾病，其特征为心室复极异常及心脏性猝死风险。导致LQTS心律失常高风险的电生理因素包括复极延长、复极离散度增加和早期后除极，临床上分别通过QT间期、T波峰至T波终点（TPE）间期以及T2/T1波幅比值进行评估。在实验性2型长QT综合征（LQT2）模型中，β受体阻滞剂可降低复极离散度并预防早期后除极。在LQT2患者的临床研究中，β受体阻滞剂对运动诱发的心脏事件比对唤醒诱发的心脏事件更有效。
本研究旨在探讨β受体阻滞剂治疗对LQT2复极特性的影响。
对25例LQT2患者在β受体阻滞剂治疗前及治疗期间通过24小时心电图记录的QT和TPE间期以及最大T2/T1波幅比值进行评估。
β受体阻滞剂治疗使最大T2/T1波幅比值从2.9±1.1降至1.8±0.7（P<.001），但未改变早搏诱发的T2/T1波幅比值。用药后，心率≥75次/分时的突发最大TPE间期缩短，心率为100次/分时的最大QT间期缩短。
β受体阻滞剂通过减少心电图早期后除极以及减少心率升高时心电图复极离散度和心室复极持续时间的突然延长，从而稳定LQT2患者的心室复极。β受体阻滞剂对早搏诱发的心电图早期后除极的作用较弱。这些发现为β受体阻滞剂对LQT2患者运动诱发的心脏事件的保护作用提供了心电图学解释。
