Estimation of intraoperative aortocoronary bypass saphenous vein graft circumference from its preoperative compliance

The aim of this study was to determine if the intraoperative circumference of aortocoronary saphenous vein bypass grafts could be predicted from preoperative measurement with B-mode ultrasound sonography in 50 patients. The circumference of the saphenous vein was measured during stepwise increments of a thigh congestive cuff from 0 to 60 mmHg. The circumference of the corresponding segment of the coronary bypass vein graft was measured intraoperatively with callipers. The intraoperative circumference was higher (11.8+/-2.3 mm) than the preoperative circumference (10.2+/-2.4 mm, P=0.006) matched to its corresponding intraoperative mean arterial pressure (57+/-15 mmHg). The prediction of the intraoperative circumference by estimation from the preoperative pressure-circumference relationship fitted by a linear model (r = 0.412, P = 0.004) did not improve on the preoperative circumference matched by arterial pressure alone (r = 0.429, P = 0.003). The intraoperative circumference of the graft vein exceeded its preoperative circumference by 12%. Prediction of the intraoperative graft vein circumference is underestimated by a linear model of its preoperative compliance.