Relation of myocardial salvage to size of myocardium at risk in dogs.

Infarct size varies in untreated animals subjected to coronary artery occlusion at the same anatomic site. The relation between the hypoperfused zone and the magnitude of myocardial salvage when different pharmacologic interventions are used remains to be established. Thus, in 95 anesthetized dogs, 1 minute after left anterior descending coronary occlusion, technetium-99m-labeled albumin microspheres (8 mCi) were injected into left atrium for the assessment of the hypoperfused zone. Fifteen minutes after coronary occlusion 42 dogs were randomized into a control group and 53 into a treated group. In the treated group, 6 dogs received nifedipine, 0.35 micrograms/kg followed by 2.4 micrograms/kg/hour; 7 received diltiazem, 0.2 mg/kg followed by 0.9 mg/kg/hour; 13 received bepridil, 2.5 mg/kg; 9 received cytochrome C, 2.5 mg/kg; 8 received rutosides, 200 mg/kg; and 10 received nifedipine plus cytochrome C. All drugs were administered intravenously. At 6 hours the dogs were killed and their hearts were cut into 3-mm-thick slices. Infarct size was determined by triphenyltetrazolium chloride staining; the hypoperfused zone was delineated by autoradiography. The dogs were retrospectively subgrouped as follows: those with small hypoperfused zones, i.e., less than 15% of the left ventricle (controls n = 8, treated n = 7) and those with large hypoperfused zones, i.e., more than 15% of the left ventricle (controls n = 34, treated n = 46). In dogs with large hypoperfused zones, treatment salvaged 42 +/- 3% of the myocardium destined to undergo necrosis, whereas in those with small hypoperfused zones 78 +/- 10% of myocardium was salvaged (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)