The branching pattern of epicardial coronary arteries is clearly three-dimensional with correspondingly complex flow patterns. The objective of the present study was to perform a detailed hemodynamic analysis using 3-D finite element method (FEM) in a LAD epicardial arterial tree including main trunk and primary branches, based on CT scans. The inlet LAD flow velocity was measured in an anesthetized pig and the outlet pressure boundary condition was estimated based on scaling laws. The spatial and temporal wall shear stress (WSS), gradient of WSS (WSSG), and oscillatory shear index (OSI) were calculated and used to identify regions of flow disturbances in the vicinity of primary bifurcations. We found that low WSS and high OSI coincide with disturbed flows (stagnated, secondary, and reversed flows) opposite to the flow divider and lateral to the junction orifice of main trunk and primary branches. High time-averaged WSSG occurs in regions of bifurcations with the flow divider having maximum values. Low WSS and high OSI were found to be related through a power law relationship. Furthermore, zones of low time-averaged WSS and high OSI amplified for larger diameter ratio and high inlet flow rate. Hence, different focal atherosclerotic-prone regions may be explained by different physical mechanism associated with certain critical levels of low WSS, high OSI, and high WSSG, which are strongly affected by the diameter ratio. The implications of the flow patterns for atherogenesis are enumerated.