Comparison of active and passive coronary perfusion in off-pump coronary artery bypass grafting

The myocardial protective effects of active and passive coronary perfusion were compared during off-pump coronary artery bypass grafting (OPCAB) in coronary stenosis model. An internal shunt tube was placed in the proximal left anterior descending arteries of adult dogs to produce a 75% coronary stenosis model. In 10 animals passive coronary perfusion was performed using an internal shunt tube placed in a pseudo-anastomotic site, and active coronary perfusion was performed through an external shunt tube. Ischemia was examined at normal and low blood pressure, based on hemodynamics, regional myocardial blood flow, and oxygen and lactate extraction in the perfused area. With passive perfusion, regional myocardial blood flow decreased and oxygen extraction and regional lactate production increased at normal blood pressure, indicating myocardial ischemia. Regional myocardial blood flow further decreased at low blood pressure. In contrast, regional myocardial blood flow with active perfusion did not change at normal or low blood pressure, and oxygen and lactate extraction were unchanged, indicating prevention of myocardial ischemia. Myocardial ischemia can occur with passive perfusion even at normal blood pressure. Active coronary perfusion that provides sufficient regional perfusion prevents myocardial ischemia during coronary artery anastomosis in OPCAB.