To avoid myocardial ischemia during off-pump coronary artery bypass, we developed a coronary active perfusion system (CAPS) that perfuses arterial blood to the coronary artery at the diastolic phase of the cardiac cycle by a syringe pump system. We report herein the details and compare CAPS with a passive shunt circuit from the femoral artery (FA shunt), regarding the physiology of the coronary artery. Six pigs were used for this study. After CAPS or FA shunt perfusion was established, coronary flow and coronary pressure were measured. The coronary flows in the native coronary artery, FA shunt perfusion, and CAPS perfusion with syringe pump stroke volume settings ranging from 0.1 to 0.4 ml were 27.2+/-3.0, 4.1+/-1.5, 12.7+/-1.2, 24.8+/-1.9, 33.3+/-1.6, and 42.2+/-1.9 ml/min, respectively. Mean coronary pressures under FA shunt perfusion and CAPS perfusion with stroke settings from 0.1 to 0.4 ml were 23.7+/-4.6, 48.8+/-5.0, 61.3+/-7.5, 70.8+/-5.4, and 82.3+/-5.2 mm Hg, respectively. CAPS had an advantage over the FA shunt regarding coronary flow with safe coronary pressure. Using CAPS, an off-pump coronary artery bypass can be performed safely without myocardial ischemia.