Effects of partial obstruction on phasic flow in aortocoronary grafts.

Phasic blood flow recorded in five unobstructed dog aortocoronary bypass grafts to the left coronary artery was similar to that of normal coronary arteries, with a high diastolic-to-systolic flow ratio which averaged 2.7 +/- 0.4. With an average of 52 +/- 7% and 72 +/- 6% stenosis in the coronary artery distal to the graft, the phasic graft-flow pattern was altered, with a decrease in the diastolic-to-systolic flow ratio to 1.9 +/- 0.4 and 1.2 +/- 0.4, respectively. Phasic patterns recorded in 42 human saphenous vein grafts to branches of the left coronary artery subsequently shown to be patent by postoperative coronary arteriography were similar to those of a normal coronary artery, with an average diastolic-to-systolic flow ratio of 2.3 +/- 0.83 and an average flow of 76 +/- 48 ml/min. Phasic flow measured in 20 grafts shown to be occulded at restudy had an average diastolic-to-systolic flow of 1.3 +/- 0.45, with an average flow of 72 +/- 33 ml/min and a phasic graft flow which was similar to that obtained from partially obstructed coronary arteries. We conclude that partial obstruction of the graft or the distal coronary artery alters the flow pattern, and this partial obstruction may lead to closure of the graft.