Abstract
Atherosclerosis occurs at favored sites. According to Fry's hypothesis, the early atherosclerotic lesions are to be expected in high shear stress area. On the other hand, Caro proposed that the early lessons should develop in the region compatible with low shear. We examined the intimal thickening of carotid arteries collecting from autopsy specimens grossly and microscopically.
We showed that the early lesions of atherosclerosis was more prominent on the outer walls of the carotid bifurcations, compared to the inner walls. Shear stress on the outer walls is said to be relatively lower than the inner ones. So, our result is in accordance with Caro's hypothesis.
With the same materials, we measured the bifurcation angles of the carotid arteries. The average of the bifurcation angles of left carotid arteries was 7 degrees wider than the right (p<0.05). The discrepancy between left and right angles was thought to be related to the anatomical position. Restricted to carotid arteries, degree of bifurcation angles seems no relation to atherosclerosis.
The intimal thickening on low shear regions was compared between the internal carotid and left anterior descending arteries (LAD). Shear rate of LAD is said be lower along the myocardial sites than along epicardial sites of the vessels. Intimal thickening of the inner walls of LAD was recognized even in infantile cases. Grading for the intimal thickening of LAD was 10 year-advanced, comparing to internal carotid arteries. Then, the development of atherosclerosis of internal carotid arteries would progress more slowly than coronary arteries.
