Effects of captopril on limiting infarct size in conscious dogs

The effects of angiotensin-converting enzyme inhibitor captopril on infarct size and cardiovascular hemodynamics were studied in 35 conscious dogs subjected to 24 h of coronary occlusion. Following occlusion of the left anterior descending coronary artery, 10 dogs were infused with captopril 0.25 mg/kg/h i.v. (group 1), eight dogs received captopril 0.5 mg/kg/h i.v. (group 2), and 17 dogs served as saline-infused controls. All infusions were started 10 min following occlusion and continued for 15 h. Eighty-eight percent of untreated dogs and 80% of group 1 captopril dogs survived the 24-h duration of the study. No experimental deaths occurred in group 2 captopril dogs. Arterial blood pressure had decreased 10-12 mm Hg in both captopril groups by 4 h and remained relatively stable for the remainder of the study period. In untreated dogs, blood pressure was unchanged for 6 h, then began a gradual decline. There were no significant differences in infarct size among the groups. When infarct size is expressed as percent of left ventricle at risk the values were: control, 39.9 +/- 5.6; captopril group 1, 44.8 +/- 4.9; and captopril group 2, 43.8 +/- 7.8%. Creatine kinase levels were not different among the groups. Heart rate and incidence of arrhythmias also did not differ among the groups. These data show that captopril had no detrimental or beneficial effects on infarct size or on cardiovascular hemodynamics associated with myocardial infarction in conscious dogs.