Changes in experimental atherosclerotic lesions of rat heart valves following long-term regression

Regression of experimental atherosclerotic lesions of rat heart valves was studied in a long-term experiment. Following a period of regression of 12 months duration, the thick superficial layers of foam cells disappeared completely. Persisting masses of cholesterol crystals did not seem to be accompanied by any cellular proliferation or fibrous reaction. Such cholesterol deposits showed peculiar transparent cystoid areas probably representing local cholesterol dissolution. The structural differences between arterial and valvular plaques can be hypothetically explained by small numbers of smooth muscle cells in the heart valves.