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 t he first lumbar level (DAG), analogous to a right gastroepiploic arter y, and an internal thoracic artery (ITA) were anastomosed to each othe r. The composite graft was anastomosed to the left anterior descending coronary artery, and then the left anterior descending coronary arter y was ligated. Before grafting, the AAG showed high sustained diastoli c pressure, but the ITA and DAG showed rapid fall of diastolic pressur es. 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 marke dly greater than in the ITA or the DAG. After grafting to the left ant erior descending coronary artery, no changes were observed in diastoli c pressures compared with the pregrafting values. Total blood flows we re 72 +/- 6, 80 +/- 7, 57 +/- 7, and 44 +/- 6 mL/min in the left anter ior 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 diasto lic graft flow (Y) were Y = 0.46X + 8.6 (r = 0. 79; p < 0.01) in the A AG, 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 indicat e that arterial grafts have disadvantages over ascending aorta-origina ted grafts in the ability to supply blood to the diastolic-dominant co ronary circulation.