Peripheral venous retroperfusion: Implications for critical limb ischemia and salvage

Arika D Kemp, Purdue University

Abstract

Peripheral arterial disease is caused by plaque buildup in the peripheral arteries. Standard treatments are available when the blockage is proximal and focal, however when distal and diffuse the same type of the treatment options are not beneficial due to the diseased locations. Restoration of blood flow and further salvaging of the limb in these patients can occur in a retrograde manner through the venous system, called retroperfusion or arteriovenous reversal. Retroperfusion has been explored over the last century, where early side to side artery to venous connections had issues with valve competency prohibiting distal flows, edema buildup, and heart failure. However, more recent clinical studies create a bypass to a foot vein to ensure distal flows, and though the results have been promising, it requires a lengthy invasive procedure. It is our belief that the concerns of both retroperfusion approaches can be overcome in a minimally invasive/catheter based approach in which the catheter is engineered to a specific resistance that avoids edema and the perfusion location allows for valves to be passable and flow to reach distally. In this approach, the pressure flow relations were characterized in the retroperfused venous system in ex-vivo canine legs to locate the optimal perfusion location followed by in-vivo validation of canines. Six canines were acutely injured for 1-3 hours by surgical ligation of the terminal aorta and both external iliac arteries. Retroperfusion was successfully performed on five of the dogs at the venous popliteal bifurcation for approximately one hour, where flow rates at peak pressures reached near half of forward flow (37±3 vs. 84±27ml/min) and from which the slope of the P/F curves displayed a retro venous vasculature resistance that was used to calculate the optimal catheter resistance. To assess differences in regional perfusion, microspheres were passed during retroperfusion and compared to baseline microspheres passed arterially prior to occlusion in which the ratio of retroperfusion and forward perfusion levels were near the ratio of reversed and forward venous flow (0.44) throughout the limb. Decreases in critical metabolites during injury trended towards normal levels post-retroperfusion. By identifying the popliteal bifurication as a perfusion site to restore blood flow in the entirety of the distal ischemic limb, showing reversal of injury, and knowing what catheter resistances to target for further chronic studies, steps towards controlled retroperfusion and thus more efficient treatment options can be made for severe PAD patients.

Degree

M.S.B.M.E.

Advisors

Kassab, Purdue University.

Subject Area

Engineering|Biomedical engineering|Physiology

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