Changes of the internal diameter of coronary artery bypass grafts in the postoperative course: Assessment based on X-ray computed tomography

Abstract

The authors used x-ray computed tomography (x-ray CT) for following up the changes of the internal diameter of coronary artery bypass grafts. After the level of the bifurcation of the truncus pulmonalis had been detected by localizing scans from the ascending aorta to the apex of the left ventricle (scanning time, three seconds; slice thickness, 5 mm) 30 mL of contrast medium was injected at a rate of 3 mL/sec via the antecubital vein. Five scans were obtained consecutively, starting eight seconds after initiation of the contrast medium injection. On the basis of two x-ray CT scans (for ± six and thirty-six ± twenty months after surgery) and a selective graft angiogram (twelve ± fifteen months after surgery), 21 patients (20 men, mean age fifty-five ± eight years) were included with a total of 35 saphenous vein grafts. The findings were compared with intraoperative electromagnetic flow meter measurements.

Results: The mean internal diameter of the 28 grafts that were patent at the time of the late x-ray CT was 4.9±1.9 mm. This was significantly (P<0.01) smaller than the mean internal diameter at the time of the early x-ray CT (5.9±1.9 mm). The internal diameter of 18 grafts had decreased, 8 had remained unchanged, and 2 had increased. A significant correlation between the graft flow rate and the internal diameter did not exist. All 7 grafts that were occluded at the time of the late scans could not be visualized in any slice of the nonenhanced or of the contrast-enhanced x-ray CT.

Conclusions: The internal diameter of grafts frequently decreases in the late postoperative period and shows no significant correlation with the graft flow rate. Occluded grafts cannot be visualized by x-ray CT.