Coronary artery disease contributes to a third of global deaths, afflicting seventeen million individuals in the United States alone. To understand the role of hemodynamics in coronary artery disease and better predict the outcomes of interventions, computational simulations of blood flow can be used to quantify coronary flow and pressure realistically. In this study, we developed a method that predicts coronary flow and pressure of three-dimensional epicardial coronary arteries by representing the cardiovascular system using a hybrid numerical/analytic closed loop system comprising a three dimensional model of the aorta, lumped parameter coronary vascular models to represent the coronary vascular networks, three-element Windkessel models of the rest of the systemic circulation and the pulmonary circulation, and lumped parameter models for the left and right sides of the heart. The computed coronary flow and pressure and the aortic flow and pressure waveforms were realistic as compared to literature data.