PHYSIOLOGICAL-CHARACTERISTICS OF CORONARY-ARTERY BYPASS GRAFTS

To investigate the hemodynamic characteristics of arterial grafts for coronary artery bypass grafting, we measured phasic pressure and flow patterns in three types of grafts in a canine model (n = 18). A graft from the ascending aorta (AAG), a graft from the descending aorta at the first lumbar level (DAG), analogous to a right gastroepiploic artery, and an internal thoracic artery (ITA) were anastomosed to each other. The composite graft was anastomosed to the left anterior descending coronary artery, and then the left anterior descending coronary artery was ligated. Before grafting, the AAG showed high sustained diastolic pressure, but the ITA and DAG showed rapid fall of diastolic pressures. Mean diastolic pressures were 83 +/- 2, 72 +/- 3, and 57 +/- 2 mm Hg in the AAG, ITA, and DAG (p < 0.05). Free flow in the AAG was markedly greater than in the ITA or the DAG. After grafting to the left anterior descending coronary artery, no changes were observed in diastolic pressures compared with the pregrafting values. Total blood flows were 72 +/- 6, 80 +/- 7, 57 +/- 7, and 44 +/- 6 mL/min in the left anterior descending coronary artery, AAG, ITA, and DAG, respectively. There were no differences in systolic graft flow between the three types of grafts. Diastolic blood flow in the ITA (29 +/- 4 mL/min) and DAG (18 +/- 3 mL/min) was smaller than in the AAG (48 +/- 4 mL/min) (p < 0.01). Regression equations between mean diastolic pressure (X) and diastolic graft flow (Y) were Y = 0.46X + 8.6 (r = 0. 79; p < 0.01) in the AAG, Y = 1.3X - 68 (r = 0.83; p < 0.001) in the ITA, and Y = 1.2X - 54 (r = 0.91; p < 0.0001) in the DAG, respectively. These results indicate that arterial grafts have disadvantages over ascending aorta-originated grafts in the ability to supply blood to the diastolic-dominant coronary circulation.