Assessment of flow velocity in saphenous vein graft using the Doppler guidewire

The purpose of the study is to evaluate flow velocity characteristics in saphenous vein graft for coronary artery bypass grafting, especially in the graftnative vessel anastomotic site. The flow velocity was measured in 13 patients with saphenous vein graft (Group I) using a Doppler guidewire, and values were compared with those in patients who had severe (≥75%, Group II, n = 31) or intermediate (<75%, Group III, n = 27) coronary artery stenosis. In Group I, the flow velocity data were measured in the graft, in the anastomotic site, and in the native artery distal to the anastomosis, and in Groups II and III data were measured proximal to the stenosis, in the stenosis, and distal to the stenosis. In the saphenous vein graft, average peak velocity (APV) was significantly lower than that proximal to the stenosis. The APV increased significantly from the graft to the anastomotic site (13.3 ± 7.2 → 36.2 ± 15.8 cm/s,p < 0.001). The APV in the anastomotic site was significantly lower than that in the stenotic site in Group II (Group II: 100.5 ± 54.7 cm/s,p < 0.001), but it was similar to that in Group III (Group III: 58.6 ± 25.2 cm/s). The APV distal to the anastomosis in Group I was normal (22.4 ± 8.0 cm/s), and it was significantly faster than the APV distal to the stenosis in Group II (Group II: 11.7 ± 8.0 cm/s,p <0.001) or Group III (Group III: 15.9 ± 8.2 cm/s,p < 0.05). In Group I, the diameter of saphenous vein graft was significantly larger than that of the native distal artery (4.23 ± 0.85 vs 2.06 ± 0.17 mm,p < 0.001), and the Doppler-derived percent cross-sectional area stenosis at the anastomosis showed a significant correlation with the angiographically derived percent crosssectional area stenosis of the graft to the native distal artery (r = 0.95,p <0.001). From these results it was thought that the increase of the APV from the graft to the anastomosis was due to caliber change from the graft to the native artery.