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 befo re the onset of acute myocardial infarction can actually preserve post ischemic 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 ischem ic insult, an effect termed ischemic preconditioning. However, no clin ical 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 patient s had total occlusion of the proximal or medial portion of the left an terior descending coronary artery and achieved reflow within 6 h of on set. Patients were classified into three groups on the basis of durati on of antecedent angina pectoris: group 1 = no angina (37 patients); g roup 2 = new angina pectoris occurring less than or equal to 7 days of onset of infarction (22 patients); group 3 = angina pectoris beginnin g >7 days before onset of infarction (25 patients). All patients under went 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 c enterline method. Results. Angiographic collateral flow grade was high er in group 3 than in groups 1 and 2 ([mean +/- SD] group 1 = 0.8 +/- 0.7, group 2 = 0.7 +/- 0.7, group 3 = 1.5 +/- 0.8). Although there wer e no differences in baseline ejection fraction and regional wall motio n among the three groups, the degree of improvement was signifi cantly greater in groups 2 and 3 than in group 1 (late minus baseline ejecti on 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 regiona l wall motion: group 1 = 0.3 +/- 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 si gnificant improvement in wall motion. Angina pectoris within 24 h befo re onset of infarction was more frequent in group 2 (82%) than group 3 (28%, p < 0.05). Conclusions. Episodes of angina pectoris occurring s hortly before the onset of infarction may preserve myocardial contract ile function in reperfused myocardial infarction despite less support from collateral flow channels, although these are suggestive results i n a limited number of patients.