Reduced microvascular and myocardial damage in patients with acute myocardial infarction and preinfarction angina

Background After acute myocardial infarction, the presence of ischemic preconditioning as a result of preinfarction angina has a protective role, limiting necrosis extent and guaranteeing greater myocardial functional recovery. The relationship between preinfarction angina, microvascular reflow, and myocardial function is poorly known. We hypothesized that after acute myocardial infarction patients with preinfarction angina have both microvascular integrity and myocardial function preservation. Methods and Results In 51 patients with a first acute myocardial infarction, we noninvasively assessed microvascular perfusion and coronary flow reserve with intravenous myocardial contrast echocardiography and investigated myocardial contractile recovery with low-dose dobutamine and 90-day follow-up echocardiography. Typical angina was present in 25 patients and absent,in 26 patients during the 7 days preceding the myocardial infarction. Compared with those patients without preinfarction angina, patients with preinfarction angina showed, a greater microvascular reflow extent and coronary flow reserve (respectively, 25.2%+/-22.8% vs 48.3%+/-23.3%, P<.05, and 3.44 +/- 0.75 vs 1.95 +/- 0.67, P<.0001), a better regional myocardial function, as expressed with wall motion score index in the risk area at dobutamine (1.67+/-0.61 vs 2.10+/-0.43, P<.005) and at follow-up (1.72 +/- 0.56 vs 2.22 +/- 0.40, P<.0001) echocardiogram, despite being similar in the first echocardiogram (2.60+/-0.28 vs 2.63+/-0.28, P=not,significant), and significantly less pronounced left ventricular dilation at follow-up. Conclusion Presence of preinfarction angina, because of the preconditioning effect, reduces myocardial damage and favors myocardial viability, limiting left ventricular remodeling. This beneficial effect seems to be at least partly mediated by the more preserved microvascular integrity and functional vasodilation after acute myocardial infarction.