Flow in Coronary Bypass Conduits On-Pump and Off-Pump

Background The purpose of the study was to measure the blood flow in coronary artery bypass grafting conduits on-pump and off-pump and to estimate the total conduit flow. Methods In a 3.5-year period, 120 patients having coronary artery bypass grafting on-pump and 97 patients having coronary artery bypass grafting off-pump with the left internal mammary artery anastomosed to the left anterior descending artery and saphenous vein grafts to the remaining diseased coronary arteries were included in the study. Flow in the bypass conduits was measured with the transit-time method. Results In men the left internal mammary artery flow (mean ± standard error of the mean) was 33.7 ± 2.0 mL/min on-pump and 34.4 ± 2.9 off-pump ( p > 0.05). In women the left internal mammary artery flow was 29.4 ± 3.0 mL/min on-pump and 22.8 ± 1.9 mL/min off-pump ( p > 0.05). In men the vein graft flow per anastomosis was 30.4 ± 1.3 mL/min on-pump and 37.8 ± 5.4 mL/min off-pump ( p > 0.05). In women the vein graft flow per anastomosis was 28.0 ± 2.9 mL/min on-pump and 23.2 ± 2.9 mL/min off-pump ( p > 0.05). Consistently in women, the mean conduit flows were numerically lower than in men. In patients undergoing coronary artery bypass grafting on-pump the total conduit flows (left internal mammary artery plus vein grafts) were 131.4 ± 2.5 mL/min in men and 108.4 ± 3.2 mL/min in women. Conclusions There were no major differences in conduit flow on-pump versus off-pump. Conventional coronary artery bypass grafting on-pump may restore up to approximately half of the normal resting coronary artery blood flow (250 mL/min).