Hemodynamic and morphologic features of arteriovenous angioaccess loop grafts.

Bilateral femoral A-VLG (5 acute, 5 chronic) were implanted in 10 dogs (e-PTFE, 6 mm ID, 25 cm length). Acute studies included measurements of cardiac output (CO) and systemic vascular resistance (SVR). Blood pressure and pressure waveforms in the graft were obtained by retrograde catheterization and pull-back readings. Chronic dogs were sacrificed 8 wks postimplant; samples were obtained following a standardized protocol and studied by light microscopy (LM) and scanning electron microscopy (SEM). Hemodynamic data show a rise in CO, a decline in SVR and a high flow through each graft. Pull-back readings show a gradual drop in pressure and loss of pulsatility from the arterial to the venous side of the graft. LM studies show IH primarily in the proximal vein. SEM showed limited pannus ingrowth endothelium close to the anastomoses and otherwise a thrombus layer throughout the lumen. A-VLG are associated with high flow, pressure drop and loss of pulsatility. Proximal vein IH is a reproducible lesion. We conclude there is severe hemodynamic stress from disturbed flow and high flow velocity and it plays a critical role in the development of venous intimal hyperplasia in AV loop grafts.