Orsini E, Lattanzi F, Reisenhofer B, Tartarini G
Division of Cardiology, ASL 5 of Pisa, Hospital F. Lotti, Pontedera, Italy.
Ital Heart J. 2001 Jul;2(7):529-38.
Exercise-induced ST-segment elevation in Q-wave leads has been traditionally associated with passive stretching of the infarct wall, perinecrotic ischemia and, according to recent scintigraphic studies, with myocardial viability. At present, however, no definitive conclusions are available. We evaluated the potential role of a time-domain analysis of exercise-induced ST-segment elevation for the identification of viable myocardium and residual ischemia in patients with previous Q-wave myocardial infarction.
Sixty patients with a previous Q-wave myocardial infarction underwent a bicycle exercise stress test, dobutamine stress echocardiography, coronary arteriography and left ventriculography.
Patients with exercise-induced ST-segment elevation in Q-wave leads (n = 36) showed more severe impairment of resting left ventricular function, when evaluated in terms of wall motion score index at echocardiography (1.62 +/- 0.33 vs 1.41 +/- 0.22, p < 0.01) and in terms of wall motion score at ventriculography (5.9 +/- 1.6 vs 4.1 +/- 1.5, p < 0.03), compared to patients without ST-segment shift (n = 24). No differences between the two groups were seen in the severity and extension of coronary artery disease. The two groups of patients did not differ in the overall incidence of viability (50% in patients with vs 62% in those without ST-segment elevation, p = NS) and homozonal ischemia (39 vs 26%, p = NS), when evaluated with dobutamine echocardiography. However, a time-domain analysis of the ST-segment changes during exercise showed that the duration of exercise up to 0.1 mV ST-segment elevation was significantly lower in patients with viability (6.2 +/- 3.3 min) than in those without (10.2 +/- 2.2 min) (p < 0.001). Accordingly, ST-segment elevation occurred within 3 and 6 min of exercise in 7/18 and in 12/18 patients with viability respectively, but in only 0/18 (p < 0.01) and in 1/18 (p < 0.01) patients without viability. Thus, ST-segment elevation occurring within the first two stages of the exercise test was, respectively, 39 and 67% sensitive and 100 and 94% specific for viability. Early onset ST-segment elevation (within 3 and 6 min) was also more frequent in patients with high-dose dobutamine-induced homozonal ischemia than in those without (sensitivity for ischemia 50 and 67%; specificity 95 and 74%, respectively).
After myocardial infarction, ST-segment elevation in Q-wave leads at the peak of exercise is associated with severe resting left ventricular dysfunction but fails to identify patients with a viable myocardium or residual ischemia. Instead, ST-segment elevation occurring in the early phases of exercise is a highly specific, although not very sensitive marker of dobutamine-assessed viability in the infarct area and may be indicative of residual ischemia.
Q波导联运动诱发的ST段抬高传统上与梗死心肌壁的被动拉伸、梗死周围缺血有关，并且根据最近的闪烁扫描研究，还与心肌存活有关。然而，目前尚无定论。我们评估了运动诱发ST段抬高的时域分析在识别既往有Q波心肌梗死患者存活心肌和残余缺血方面的潜在作用。
60例既往有Q波心肌梗死的患者接受了自行车运动负荷试验、多巴酚丁胺负荷超声心动图检查、冠状动脉造影和左心室造影。
与无ST段移位的患者（n = 24）相比，Q波导联运动诱发ST段抬高的患者（n = 36）在静息左心室功能方面表现出更严重的损害，通过超声心动图评估的室壁运动评分指数（1.62±0.33对1.41±0.22，p < 0.01）以及通过心室造影评估的室壁运动评分（5.9±1.6对4.1±1.5，p < 0.03）。两组患者在冠状动脉疾病的严重程度和范围方面无差异。当通过多巴酚丁胺超声心动图评估时，两组患者在存活心肌的总体发生率（有ST段抬高患者为50%，无ST段抬高患者为62%，p = 无显著差异）和同向性缺血发生率（39%对26%，p = 无显著差异）方面没有差异。然而，运动期间ST段变化的时域分析显示，有存活心肌的患者达到ST段抬高0.1 mV的运动持续时间（6.2±3.3分钟）显著低于无存活心肌的患者（10.2±2.2分钟）（p < 0.001）。因此，有存活心肌的患者中分别有7/18和12/18在运动3分钟和6分钟内出现ST段抬高，但无存活心肌的患者中分别只有0/18（p < 0.01）和1/18（p < 0.01）出现。因此，运动试验前两个阶段出现的ST段抬高对存活心肌的敏感性分别为39%和67%，特异性分别为100%和94%。高剂量多巴酚丁胺诱发同向性缺血的患者中，早期出现ST段抬高（3分钟和6分钟内）也比无缺血患者更常见（缺血敏感性分别为50%和67%；特异性分别为95%和74%）。
心肌梗死后，运动高峰时Q波导联ST段抬高与严重的静息左心室功能障碍相关，但无法识别有存活心肌或残余缺血的患者。相反，运动早期出现的ST段抬高是梗死区域多巴酚丁胺评估存活心肌的高度特异性指标，尽管不太敏感，并且可能提示残余缺血。
