Significance of preinfarction angina for preservation of left ventricular function in acute myocardial infarction

The effect of preinfarction angina on the preservation of left ventricular function was evaluated with the use of cineventriculography in 37 patients who had either total or subtotal occlusion of the proximal left anterior descending coronary artery during the convalescent period of myocardial infarction. In 15 patients who had preinfarction angina more than 1 week before the onset of acute myocardial infarction (group A), the global left ventricular ejection fraction was 54 ± 3% (SEM) and regional wall motion in the infarct area was 10 ± 3%. In 10 patients who had preinfarction angina occurred within 1 week before the onset of acute myocardial infarction (group B), the left ventricular ejection fraction and regional wall motion in the infarct area were 42 ± 3% and 1 ± 2%, respectively. In 12 patients without preinfarction angina (group C), the left ventricular ejection fraction and regional wall motion in the infarct area were 38 ± 3% and −1 ± 2%, respectively. In groups B and C, both the left ventricular ejection fraction and regional wall motion in the infarct area were lower than those in group A ( p < 0.05). The collateral circulation at the onset of acute myocardial infarction was better in group A compared with groups B and C ( p < 0.05). Thus the collateral circulation, promoted by repetitive anginal episodes indicative of myocardial ischemia, causes the preservation of myocardial function.