The effect of intracoronary diltiazem on regional myocardial function and development of infarcts in porcine hearts

The effect of intracoronary (i.c.) pretreatment with diltiazem on regional myocardial function and the development of infarcts was investigated in regionally ischemic, reperfused porcine hearts. The left anterior descending coronary artery (LAD) was distally ligated in 16 pigs for 20-90 min followed by 24 h of reperfusion. Eight pigs were treated with increasing doses of i.c. diltiazem (0.375 mg/min, 0.75 mg/min, 1 mg/min) prior to ischemia. Eight pigs served as controls. Regional myocardial function was assessed by implanted ultrasonic crystals. Infarct size was determined as ratio of infarcted (tetrazolium stain) to ischemic myocardium (dye technique). I.c. diltiazem mainly depressed early systolic shortening (isovolumetric contraction) and lengthening during the first half of diastole. Pretreatment with this calcium antagonist significantly delayed the development of infarcts. In control experiments, a mean infarct size of 74% was found after 45-min ischemia. At that time no infarction was observed in the treated group, where infarcts started to evolve after 60-min ischemia. It is concluded that the favorable action of i.c. diltiazem can mainly be ascribed to a reduced myocardial oxygen consumption at the onset of ischemia.