Hohnloser S H, Klingenheben T
University Hospital, Department of Cardiology, Freiburg, Germany.
Pacing Clin Electrophysiol. 1994 Mar;17(3 Pt 2):428-33. doi: 10.1111/j.1540-8159.1994.tb01409.x.
Sudden cardiac death continues to be a poorly understood event in terms of its underlying pathophysiological mechanisms. The observation of a circadian variability in the incidence of this catastrophic event with a prominent peak in the early morning hours provides an opportunity to study triggering factors that may play a causative role in the genesis of sudden cardiac death. As reviewed in this article, there is convincing evidence that transient disturbances in autonomic tone and the resulting consequences may predispose the heart to increased electrical vulnerability. This evidence is based for instance on circadian fluctuations of spontaneous ventricular ectopic activity and transient ischemia, which may serve as trigger factors for the genesis of sustained ventricular tachyarrhythmias. Analysis of heart rate variability provides further evidence of reduced vagal and elevated sympathetic tone during the morning hours particularly in patients with compromised left ventricular function. Diurnal variations in ventricular repolarization as indicated by QT interval changes in the surface ECG also support the concept of triggering factors in the genesis of sudden cardiac death. Therapeutic measures aiming at a reduction in sympathetic input to the heart have been successful in preventing ventricular fibrillation and thus indicate the importance of unbalanced sympathetic tone in patients prone to sudden cardiac death.
就心脏性猝死潜在的病理生理机制而言，它仍然是一个了解甚少的事件。观察到这一灾难性事件的发生率存在昼夜变化，且在清晨时分有一个显著的峰值，这为研究可能在心脏性猝死发生过程中起因果作用的触发因素提供了机会。正如本文所综述的，有令人信服的证据表明，自主神经张力的短暂紊乱及其产生的后果可能使心脏更容易出现电易损性增加。例如，这种证据基于自发性室性异位活动和短暂性缺血的昼夜波动，它们可能作为持续性室性快速心律失常发生的触发因素。心率变异性分析进一步证明，在早晨时段，尤其是左心室功能受损的患者，迷走神经张力降低，交感神经张力升高。体表心电图QT间期变化所显示的心室复极的昼夜变化也支持心脏性猝死发生过程中存在触发因素这一概念。旨在减少心脏交感神经输入的治疗措施已成功预防了心室颤动，因此表明交感神经张力失衡在易发生心脏性猝死的患者中的重要性。
