Intimal hyperplasia, an aberrant proliferation of smooth muscle cells that causes stenosis and graft occlusion, is the primary cause of the failure of grafts after a few years. In this way, and using the constructal design method, this study looks at how the stenosis degree, junction angle, and diameter ratio affect the flow through a bypass graft that goes around an idealised coronary artery partially blocked. The results show that the flow effect by several factors: Stenosis ratio (S), Bypass Attachment Point (L2), Bypass Angle (α), and Bypass Diameter (D1). The results indicate that the pressure drop is reduced when S is low, the optimal attachment point L2 = 4 Artery diameter (D), the optimal angle α = 30°, and the optimal D1 = 1.25D.