In vivo analysis and three-dimensional visualisation of blood flow patterns at vascular end-to-side anastomoses

The aim of this study was to describe the velocity fields at distal vascular end-to-side anastomoses with different anastomosis angles in vivo.

The abdominal aorta of ten 90 kg pigs was exposed from the superior mesenteric artery to the trifurcation. A segment of the aorta was bypassed using a polyurethane graft. Three anastomosis angles: 90 degrees (n = 3), 45 degrees (n = 3) and 15 degrees (n = 4) were studied. The bypass length, the anatomical position and the geometry of the anastomoses were standardised. During measurements, the proximal outflow segment was occluded and the flow rate was controlled by reversible iliac artery cross-clamping. Using a colour Doppler system the velocity fields were measured at various positions in the anastomosis. The colour Doppler velocity data were transferred to a computer for dynamic three-dimensional visualisation of the velocity profiles.

The angulation was reproduced within 10%. During the experiment, the flow rate was kept constant with Reynold's numbers typical for peripheral arteries. In the 90 degrees anastomoses very disturbed flow fields were seen. The 45 degrees anastomoses were characterised by: (1) low antegrade and retrograde velocities at the heel and (2) a zone of reverse and oscillating velocities at the toe and at one diameter downstream of the toe (1DDD) during deceleration. In the 15 degrees anastomoses no flow disturbances were seen either at the toe or at 1DDD. The velocity profiles were close to parabolic at peak flow at both positions.

It is concluded that the 15 degrees anastomosis is preferable from a haemodynamic point of view.