Coronary arterial ectasia, a predominant type of coronary sclerosis in aged captive rhesus monkeys (Macaca mulatta).

In hearts from aged rhesus monkeys, ranging from 20 to over 30 years, marked coronary arterial ectasia, dilatation, and tortuosity of the entire vessel were observed in 18 animals. Another 7 animals showed a moderate degree of ectatic changes. Dilated arteries showed remarkable thinness of the tunica media with atrophy and attenuation of the muscle cells and increased fibrous tissue. Diffuse or focal intimal fibrous thickening was present in the ectatic arterial wall, but cholesterol deposit, calcification, or the presence of lipid-laden foam cells in the intimal and medial wall was not observed. A focal degeneration and fibrosis of the myocardium were seen in the hearts of 11 cases. Clinically, 2 cases had either spontaneous diabetes mellitus or cardiac decompensation with mitral insufficiency, but the others had no abnormal metabolic or cardiovascular histories. Coronary arterial ectasia accompanied with medial fibrosis appears to be a predominant type of coronary arterial lesion in aged rhesus monkeys under long-term captivity.