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A Computational Study of the Factors Influencing Pressure in Arteriovenous Fistulae Venous Aneurysms

Purpose To investigate the factors influencing the hydrostatic pressure exerted within the venous aneurysms (VA) of an arteriovenous fistula (AVF). Methods Ideal models of a side-to-end brachial-cephalic AVF were computationally constructed and typical values for the length and the local diameters were considered for both the artery and vein sections of the models. Three VA configurations were reconstructed (spherical, fusiform and curved) and hydrostatic pressure was assessed with respect to different degrees of the outflow vein stenosis, ranging from 25% to 95%, and VA maximum diameters, using validated, commercially available software. Results The pressure in the VA was steady (1200 Pa) for venous outflow stenoses up to 75%. For stenoses greater than 75% a exponential pressure rise was observed, reaching 1500 Pa for stenoses of 95%. Neither the VA configuration nor its maximum diameter affected the pressure values exerted within the VA or the point of the pressure upstroke. Conclusions our study supports the presence of a critical stenotic outflow vein diameter beyond which there is an exponential VA pressure increase, influenced neither by the shape nor the size of the VA. Whether the prompt, non-invasive detection of this finding can contribute or lead to the determination of a criterion for early intervention in VAs before clinical complications are developed, should be investigated by future studies.