Blood flow-induced endothelial shear stress has strong effect on endothelial function and development or progression of plaque formation. It is extensively accepted that low and/or oscillating shear stress causes endothelial dysfunction and is one of crucial factors in localizing early atherosclerosis .In contrary, normal and high shear stress is atheroma protective and is involved in compensatory remodeling . Most studies reported that the endothelial shear stress distribution in often idealized geometrical models of human coronary arteries was the subject of numerous investigations , and in these studies it was shown that the geometry of coronary arteries is the main determinant of the observed shear stress distribution. Generally, downstream of a plaque, low shear stress can be expected, Several cardiovascular active drugs have been shown to be cardio-protective for patients with obstructive coronary disease. Of these drugs, calcium channel blocker is one of most prescribed in everyday clinical practice. Ninomiya et al. reported calcium channel blocker was associated with increased coronary diameter and blood fluid with dose-dependent pattern in patients with normal or mild stenotic coronary artery. However, no reports on the dynamic change of endothelial shear stress after calcium channel blocker in -vitron were published so far. As a result, the aim of this study was to evaluate the effect of intra-venous injection of Nicardipine, one calcium channel blocker with shorter half-time, on the re-distribution of endothelial shear stress in patients with acute coronary syndrome and mild stenotic (<50%) coronary artery disease.