Vascular Physics: Explaining the Nature of Escape Veins and When to Use Endovascular Ligation.

Small branching veins that arise from the venous outflow of surgical arterial-venous fistulas (AVFs) are frequently seen during fistulograms performed to evaluate for poorly functioning AVFs. It is hypothesized that the presence of escape veins can decrease the performance of native AVFs during hemodialysis by diverting flow. Though interventional methods for exclusion of escape veins are effective, the mechanism of disruption these small branching vessels cause on flow through AVFs is unknown. Furthermore, an objective method for identifying escape veins that cause significantly diminished venous flow has not been defined. The following describes the detrimental nature of escape veins using tenants of physics and electrical circuitry. Subsequently, the proceeding study shows the identification of small branching escape veins in patients during fistulography. Intravascular pressure measurements were obtained proximal and distal to the ostium of the offending collaterals in these patients. Escape veins causing a pressure gradient of at least 5 mmHg were treated, and pressure measurements were repeated following intervention. The patients were entered into a database and hemodialysis blood flow rates were monitored to determine if escape vein intervention increased AVF performance.