Sudden cardiac death (SCD) accounts for ∼50% of mortality after myocardial infarction (MI). Most SCDs result from ventricular tachyarrhythmias, and the tachycardias that precipitate cardiac arrest result from multiple mechanisms. As a result, it is highly unlikely that any single test will identify all patients at risk for SCD. Current guidelines for use of implantable cardioverter-defibrillators (ICDs) to prevent SCD are based primarily on measurement of left ventricular ejection fraction (LVEF). Although reduced LVEF is associated with increased total cardiac mortality after MI, the focus of current guidelines on LVEF omits ∼50% of patients who die suddenly. In addition, there is no evidence of a mechanistic link between reduced LVEF and arrhythmias. Thus, LVEF is neither sensitive nor specific as a tool for post-MI risk stratification. Newer tests to screen for predisposition to ventricular arrhythmias and SCD examine abnormalities of ventricular repolarization, autonomic nervous system function, and electrical heterogeneity. These tests, as well as older methods such as programmed stimulation, the signal-averaged electrocardiogram, and spontaneous ventricular ectopy, do not perform well in patients with LVEF ≤30%. Recent observational studies suggest, however, that these tests may have greater utility in patients with LVEF >30%. Because SCD results from multiple mechanisms, it is likely that combinations of risk factors will prove more precise for risk stratification. Prospective trials that evaluate the performance of risk stratification schema to determine ICD use are necessary for cost-effective reduction of the incidence of SCD after MI.

中文翻译：

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心肌梗死后心脏猝死的危险分层

心脏猝死（SCD）约占心肌梗死（MI）死亡率的50％。大多数SCD是由室性心律失常引起的，而导致心脏骤停的心动过速是由多种机制引起的。结果，几乎没有任何一项测试能够识别出所有有SCD风险的患者。当前使用植入式心脏复律除颤器（ICD）预防SCD的指南主要基于对左心室射血分数（LVEF）的测量。尽管左室射血分数降低与心梗后总心脏死亡率增加有关，但当前关于左室射血分数的指导原则忽略了约50％突然死亡的患者。此外，没有证据表明LVEF降低与心律不齐之间存在机械联系。因此，LVEF作为心梗后风险分层的工具既不敏感也不特定。用于筛查室性心律失常和SCD易感性的较新测试可检查室性复极，自主神经系统功能和电异质性的异常。这些测试以及较旧的方法，例如程序性刺激，平均信号心电图和自发性室性异常，在LVEF≤30％的患者中表现不佳。然而，最近的观察性研究表明，这些检查对于LVEF> 30％的患者可能具有更大的效用。由于SCD是由多种机制产生的，因此风险因素的组合可能会被证明对风险分层更为精确。评估风险分层方案的性能以确定ICD使用的前瞻性试验对于经济有效地降低MI后SCD的发生率是必要的。