Flow resistance over technical anastomoses in relation to the angle of distal end-to-side connections

Abstract

Objective - The fluid dynamics within the anastomotic region may contribute to graft failure. The aim was to investigate how flow resistance is affected by anastomotic angle and viscosity. Design - Technical end-to-side anastomoses of 3-mm inlet/outlet diameter were precision-drilled in plastic blocks at 90°, 60°, 45°, and 30° angles, with 0° as control to calculate relative resistance. Five pressure loads of 200-1000 mmH2O and two fluid viscosities were tested using pulsatile perfusion. Results - Absolute resistances showed a significant linear correlation with pressure, regardless of anastomotic angle and with similar slope values. Increased viscosity produced an upward shift in resistance but otherwise had no effect. However, the relative resistances showed transition zones at increased pressures, which were sensitive to viscosity. The 30° angle produced less resistance than steeper angles. Conclusion - Previous studies gave contradictory results about the importance of anastomotic angle. Our findings suggest that in iso-diametrical technical anastomoses a low angle is favorable. The complexity of angularity in distal aorto-coronary anastomoses was illustrated by threshold phenomena at different pressures, possibly due to induced turbulence and anastomotic resonance.