Mean flow of saphenous vein graft and its influencing factors in patients performed coronary artery bypass grafting

OBJECTIVE: To analyze the mean blood flow of saphenous vein (SV) graft and it's influencing factors in off-pump coronary artery bypass grafting by using transit-time flowmeter (TTFM). METHODS: Three hundred and twenty-six patients were studied. After all anastomoses were completed, and hemo-dynamic status was stable, TTFM was utilized to measure and record the SV flow wave, pulsatility index (PI), value of mean flow, diastolic and systolic peak flow, vascular resistance, insufficiency ratio and mean blood pressure. The standard conditions of good graft status to define the normal mean flow included good diastolic augmentation of blood wave, PI less than 5, intraoperative and postoperative no significant change in electrocardiogram, and smoothly postoperative recovery. RESULTS: Total mean flow calculated from that of all patients was (39 +/- 23) ml/min (10-153 ml/min). Majority mean value (60.1%, 196/326) was in the range of 20-50 ml/min. Statistics showed that mean flow was significantly related to vascular resistance and diastolic peak flow and PI rather than the other factors (r was -0.95, 0.77 and -0.51 respectively). CONCLUSIONS: For the patients, over 15 ml/min mean flow of SV graft is acceptable, and over 35 ml/min is satisfactory. The diastolic peak flow and vascular resistance are two important factors influencing mean flow.