Relation of atherosclerosis to arterial wall shear in the left anterior descending coronary artery of man.

Low fluid dynamic shear acting on the vascular endothelium has been suggested as a factor in atherogenesis. This study describes qualitatively differences of wall shear rate in the left anterior descending coronary artery (LAD) of man and relates the distribution of wall shear to that of atheromatous plaques. Selective coronary arteriograms of 21 patients without obstructive LAD diseases were reviewed. Blood velocity, and therefore wall shear in the LAD, was assessed qualitatively based upon the rate of clearance of contrast material. There was a rapid clearing of contrast material along the outer wall of the LAD as it curved around the border of the heart. A much slower clearing occurred along the inner wall, bordering the myocardium, which persisted two to six cardiac cycles after the outer wall had cleared. This suggests that velocity, and therefore shear rate, is lower along the inner wall of the LAD than along the outer wall. In 27 patients who died of noncardiac disease, an uneven distribution of atheromatous plaques in the LAD was observed histologically, with greater involvement of the inner wall. These observations demonstrate an association between the lower shear rate along the inner wall of the LAD and the site of higher concentration of atherosclerosis.