Longer coronary anastomosis provides lower energy loss in coronary artery bypass grafting

Distal anastomosis technique affects graft patency and long-term outcomes in coronary artery bypass grafting, however, there is no standard for the appropriate length of distal anastomosis. The purpose of this study is to evaluate whether longer distal anastomosis provides higher quality of distal anastomosis and better hemodynamic patterns. Off pump CABG training simulator, YOUCAN (EBM Corporation, Japan), was used for distal anastomosis model. Two lengths of distal anastomosis model (10 versus 4 mm) were prepared by end-to-side anastomosis technique. After CT scan constructed three-dimensional inner shape of distal anastomosis, computational flow dynamics (CFD) was used to analyze hemodynamic patterns. The working flow was defined as Newtonian fluid with density of 1050 kg/m³ and viscosity of 4 mPa s. The boundary condition was set to 100 mmHg at inlet, 50 ml/min at outlet, and 100 % stenosis of proximal coronary artery. Three-dimensional CT imaging showed quality of distal anastomosis in 10 mm model was more uniform without vessel wall inversion or kinking compared to 4 mm model. Anastomotic flow area was significantly larger in 10 mm model than that in 4 mm model (28.67 ± 4.91 versus 8.89 ± 3.18 mm², p < 0.0001). Anastomotic angle was significantly smaller in 10 mm model compared to 4 mm model (10.2 ± 5.65° versus 20.6 ± 3.31°, p < 0.0001). CFD analysis demonstrated 10 mm model had streamlined flow with smooth graft curvature, whereas 4 mm model had abrupt blood flow direction changes with flow separation at the toe. 10 mm model had significantly lower energy loss than 4 mm model (34.78 ± 6.90 versus 77.10 ± 21.47 μW, p < 0.0001). Longer distal anastomosis provided higher quality of distal anastomosis, larger anastomotic flow area, smaller anastomotic angle, and smoother graft curvatures. These factors yielded lower energy loss at distal anastomosis.