Detection of Coronary Atherosclerosis in the Living Rabbit by the Ergonovine Stress Test

Abstract

Electrocardiograms were taken before and during 15 minutes after administration of 0.05 mg/kg and, on occasion 1 mg/kg, of ergonovine maleate intravenously for a total of 94 ergonovine stress tests on 34 rabbits. Fourteen animals were controls and twenty, cholesterol fed. One series was kept on the diets for about 2.5 months and another for about 5 months. Positivity of the ergonovine stress test was indicated by a drug-induced depression of the S-T segment amounting to 0.5 mm or more below the isoelectric level in either leads II or IV. Hearts were examined microscopically, aortas grossly. In control animals, ergonovine stress tests were uniformly negative and coronary arteries and myocardium normal. In cholesterol-fed rabbits, after 2.5 months the ergonovine stress test was likewise negative but there was atherosclerosis of the thoracic aorta, diffuse fatty infiltration of the myocardium and marked cholesterolemia. After 5 months, the ergonovine stress test had become positive in all cholesterol-fed rabbits. At this time, each animal showed subendothelial lipid accumulation in the coronary arteries with occlusive intimal atherosclerosis, and in the myocardium, fatty infiltration and spotty hyaline degeneration. Data show a correlation of positivity of the ergonovine stress test with occlusive atherosclerosis of the small coronary arteries and myocardial damage. It is suggested that this test may provide an experimental procedure for the study of coronary atherosclerosis in the living animal.