A parametric numerical investigation on haemodynamics in distal coronary anastomoses

Anastomotic haemodynamics, which plays an important role in the performance of bypass graft, is known to be profoundly affected by the diameter ratio (Φ) and angle (α) between the graft and host artery in the peripheral region. We hypothesize that these geometric factors would play similar roles in distal coronary anastomoses and that they could be improved for clinical applications through parametric studies. Anastomotic models covering a range of Φ (1:1, 1.5:1 and 2:1) and α (15°, 30°, 45° and 60°) were investigated numerically in physiological coronary flow conditions. The transient flow patterns, cycle-averaged wall shear stress (WSS), oscillatory shear index (OSI), spatial and temporal WSS gradients (SWSSG and TWSSG) were compared. Results show a stronger influence of Φ than α on haemodynamics in distal coronary artery anastomoses. Substantially higher SWSSG and TSSWG occur on the artery floor when Φ = 1:1 compared to larger Φ. High levels of OSI occur in critical regions when Φ = 1:1 and 2:1. The largest area of high OSI is found in the anastomotic region when α = 15°, whereas the highest level of SWSSG appears on the artery floor when α = 60°. The study suggests the clinical relevance of optimizing geometric parameters of coronary anastomoses to improve their haemodynamic performance. We speculate that for a distal coronary anastomosis with a 20:80 proximal–distal flow division ratio maintained in the host artery, Φ = 1.5 and α = 30–45° would enhance its long-term performance.