The effect of acute hypercholesterolemia on myocardial infarct size and the no-reflow phenomenon during coronary occlusion-reperfusion.

The goal of this study was to determine the effects of acute hypercholesterolemia on the evolution of myocardial infarction in a preparation of coronary occlusion-reperfusion. New Zealand white rabbits were fed a 2% cholesterol-enriched diet for 3 days (plasma cholesterol 329 +/- 70 mg/dl), or maintained on the control diet (plasma cholesterol 67 +/- 12 mg/dl). Temporary (30 min) coronary artery occlusion was performed in open-chest rabbits with a suture snare. The snare was released to permit reperfusion. When the animals were killed 5.5 hr later, left ventricles were cut into 3 mm slices. Infarct size was determined by planimetry of tetrazolium-stained slices while the area at risk of infarction (hypoperfused zone) was determined by planimetry of the "cold spots" on autoradiograms of the slices that contained 99m Tc-labeled microspheres that had been injected 1 min after occlusion. Infarct size, expressed as percent of the hypoperfused zone, was 42.8 +/- 1.3% (n = 10) in the control group and was increased by approximately 100% in cholesterol-fed animals to 83.7 +/- 2.0% (n = 10, p less than .001). To test the hypothesis that vascular obstruction (no reflow) might account for the larger infarct size, thioflavin S was injected immediately before the animals were killed to demarcate perfused myocardium in three additional groups of animals: standard chow-fed rabbits (n = 5), cholesterol-fed rabbits (n = 5), and standard chow-fed rabbits that, in addition, received an infusion of isoproterenol (0.1 microgram/kg/min, n = 6), an intervention believed to increase infarct size through a mechanism not dependent on the no-reflow phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)