Effect of angina pectoris on myocardial protection in patients with reperfused anterior wall myocardial infarction: retrospective clinical evidence of preconditioning?

OBJECTIVES We examined whether angina pectoris occurring shortly before the onset of acute myocardial infarction can actually preserve postischemic left ventricular function in humans. BACKGROUND Experimental studies indicate that brief, transient episodes of ischemia render the heart very resistant to infarction from a subsequent sustained ischemic insult, an effect termed ischemic preconditioning. However, no clinical data are available concerning the implications of angina pectoris shortly before the onset of infarction in humans. METHODS We studied 84 patients with an acute anterior myocardial infarction. All patients had total occlusion of the proximal or medial portion of the left anterior descending coronary artery and achieved reflow within 6 h of onset. Patients were classified into three groups on the basis of duration of antecedent angina pectoris: group 1 = no angina (37 patients); group 2 = new angina pectoris occurring < or = 7 days of onset of infarction (22 patients); group 3 = angina pectoris beginning > 7 days before onset of infarction (25 patients). All patients underwent left ventriculography on the day of, and 28 days after, onset of infarction to determine ejection fraction and regional wall motion in the territory of the left anterior descending coronary artery by the centerline method. RESULTS Angiographic collateral flow grade was higher in group 3 than in groups 1 and 2 ([mean +/- SD] group 1 = 0.08 +/- 0.7, group 2 = 0.7 +/- 0.7, group 3 = 1.5 +/- 0.8). Although there were no differences in baseline ejection fraction and regional wall motion among the three groups, the degree of improvement was significantly greater in groups 2 and 3 than in group 1 (late minus baseline ejection fraction: group 1 = 0 +/- 8%, group 2 = 7 +/- 10% group 3 = 6 +/- 10% [p < 0.05 group 1 vs. groups 2 and 3]; late minus baseline regional wall motion: group 1 = 0.2 +/- 0.4, group 2 = 0.6 +/- 0.5, group 3 = 0.5 +/- 0.6 SD/chord [p < 0.05, group 1 vs. group 2]). When the study was limited to those patients with no or poor collateral flow (31 in group 1, 19 in group 2, 10 in group 3), only group 2 patients had a significant improvement in wall motion. Angina pectoris within 24 h before onset of infarction was more frequent in group 2 (82%) than group 3 (28%, p < 0.05). CONCLUSIONS Episodes of angina pectoris occurring shortly before the onset of infarction may preserve myocardial contractile function in reperfused myocardial infarction despite less support from collateral flow channels, although these are suggestive results in a limited number of patients.