IMPORTANCE OF ISCHEMIC PRECONDITIONING AND COLLATERAL CIRCULATION FORLEFT-VENTRICULAR FUNCTIONAL RECOVERY IN PATIENTS WITH SUCCESSFUL INTRACORONARY THROMBOLYSIS FOR ACUTE MYOCARDIAL-INFARCTION

We studied the effects of myocardial ischemic preconditioning and pree xistent collateral circulation on the preservation of left ventricular function in 30 patients who had successful intracoronary thrombolysis within 6 hours after the onset of a first acute anterior myocardial i nfarction. The existence of ischemic preconditioning was defined as th e episode of recurrent ischemic chest pain within 4 hours before the o nset of acute myocardial infarction. In 16 patients with ischemic prec onditioning (group A), the left ventricular ejection fraction during t he convalescence of myocardial infarction was 57% +/- 11% (mean +/- SD ); regional wall motion in the infarct area was 13% +/- 9%. In 14 pati ents without ischemic preconditioning (group B), the left ventricular ejection fraction and regional wall motion in the infarct area were 46 % +/- 9% and 5% +/- 9% (both p < 0.05 vs group A). Moreover, among gro up A patients, seven patients having a well-developed collateral circu lation during the acute stage of myocardial infarction showed a more p rominent improvement in regional wall motion in the infarct area compa red with nine patients having poor or no collateral circulation (18% /- 8% vs 9% +/- 7%, p < 0.05). These data indicate that ischemic preco nditioning is effective for the preservation of left ventricular funct ion in patients with successful intracoronary thrombolysis and that pr eexistent coronary collateral circulation potentiates this favorable e ffect of ischemic preconditioning.