Analysis of the segmental venous stenosis in blood access

During in vivo sheep studies on biolized shunts of a unique geometry it was found that venous stenosis was produced in 3 of 3 implants, suggesting its use as a model for the study of this lesion. Hemodynamic data on biolized shunts of different geometry and silicone shunts did not demonstrate significant differences among them. In general, venous side pressures were low and steady. Arterial side pressures upon stabilization were not significantly different than the controls. Time averaged hemodunamic parameters do not appear as dominant differences between the blood access devices evaluated. Angiographic studies indicated that a divergence of flow takes place at the shunt's exist and reveled angulation between the short shunt and the vein. Venous wall immobilization at increased pressures was observed. The tension which causes the wall to be immobilized is beleived to be due to anatomical mismatch between the short shunt and the vascular connection points. Although mechanical stress to the wall, fluid dynamic events and the resultant mass transport processes all may be important in causing the development of the stenotic lesion, the data to date seem to strongly implicate mechanical factors, specifically angualtion and stretching of the vein, in the development of venous stenosis. Local fluid dynamic and mass transfer effects may aggravate the already overstressed vessel.