Department of Cardiology, Institute for Surgical Research and Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet Oslo, Norway.
JACC Cardiovasc Imaging. 2013 Aug;6(8):841-50. doi: 10.1016/j.jcmg.2013.03.005. Epub 2013 Jul 10.
OBJECTIVES: The aim of this study was to test the hypothesis that strain echocardiography might improve arrhythmic risk stratification in patients after myocardial infarction (MI). BACKGROUND: Prediction of ventricular arrhythmias after MI is challenging. Left ventricular ejection fraction (LVEF) <35% is the main parameter for selecting patients for implantable cardioverter-defibrillator therapy. METHODS: In this prospective, multicenter study, 569 patients >40 days after acute MI were included, 268 of whom had ST-segment elevation MIs and 301 non-ST-segment elevation MIs. By echocardiography, global strain was assessed as average peak longitudinal systolic strain from 16 left ventricular segments. Time from the electrocardiographic R-wave to peak negative strain was assessed in each segment. Mechanical dispersion was defined as the standard deviation from these 16 time intervals, reflecting contraction heterogeneity. RESULTS: Ventricular arrhythmias, defined as sustained ventricular tachycardia or sudden death during a median 30 months (interquartile range: 18 months) of follow-up, occurred in 15 patients (3%). LVEFs were reduced (48 ± 17% vs. 55 ± 11%, p < 0.01), global strain was markedly reduced (-14.8 ± 4.7% vs. -18.2 ± 3.7%, p = 0.001), and mechanical dispersion was increased (63 ± 25 ms vs. 42 ± 17 ms, p < 0.001) in patients with arrhythmias compared with those without. Mechanical dispersion was an independent predictor of arrhythmic events (per 10-ms increase, hazard ratio: 1.7; 95% confidence interval: 1.2 to 2.5; p < 0.01). Mechanical dispersion and global strain were markers of arrhythmias in patients with non-ST-segment elevation MIs (p < 0.05 for both) and in those with LVEFs >35% (p < 0.05 for both), whereas LVEF was not (p = 0.33). A combination of mechanical dispersion and global strain showed the best positive predictive value for arrhythmic events (21%; 95% confidence interval: 6% to 46%). CONCLUSIONS: Mechanical dispersion by strain echocardiography predicted arrhythmic events independently of LVEF in this prospective, multicenter study of patients after MI. A combination of mechanical dispersion and global strain may improve the selection of patients after MI for implantable cardioverter-defibrillator therapy, particularly in patients with LVEFs >35% who did not fulfill current implantable cardioverter-defibrillator indications.
目的：本研究旨在验证应变超声心动图是否可以改善心肌梗死后（MI）患者的心律失常风险分层。
背景：预测 MI 后室性心律失常具有挑战性。左心室射血分数（LVEF）<35%是选择植入式心脏复律除颤器治疗患者的主要参数。
方法：在这项前瞻性、多中心研究中，纳入了急性 MI 后>40 天的 569 例患者，其中 268 例为 ST 段抬高型心肌梗死患者，301 例为非 ST 段抬高型心肌梗死患者。通过超声心动图评估 16 个左心室节段的平均峰值纵向收缩期应变作为整体应变。在每个节段评估心电图 R 波至最大负向应变的时间。机械离散度定义为这 16 个时间间隔的标准差，反映收缩的异质性。
结果：在中位 30 个月（四分位距：18 个月）的随访中，15 例患者（3%）发生了定义为持续性室性心动过速或猝死的心律失常。与无心律失常的患者相比，心律失常患者的 LVEF 降低（48 ± 17%比 55 ± 11%，p<0.01），整体应变明显降低（-14.8 ± 4.7%比-18.2 ± 3.7%，p=0.001），机械离散度增加（63 ± 25 ms 比 42 ± 17 ms，p<0.001）。机械离散度每增加 10 ms，心律失常事件的风险比为 1.7（95%置信区间：1.2 至 2.5；p<0.01）。机械离散度和整体应变是非 ST 段抬高型心肌梗死患者（均为 p<0.05）和 LVEF>35%患者（均为 p<0.05）心律失常的标志物，而 LVEF 则不是（p=0.33）。机械离散度和整体应变的组合对心律失常事件具有最佳的阳性预测值（21%；95%置信区间：6%至 46%）。
结论：在这项前瞻性、多中心 MI 后患者研究中，应变超声心动图的机械离散度独立于 LVEF 预测心律失常事件。机械离散度和整体应变的组合可能改善 MI 后患者植入式心脏复律除颤器治疗的选择，尤其是在不符合当前植入式心脏复律除颤器适应证但 LVEF>35%的患者中。
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