Microvascular in-vivo Analysis of Retrograde Venous Arterialization of Ischemic Skeletal Muscle

Abstract

Objective: Nearly 20% of patients with critical limb ischemia will not be suitable for arterial bypass due to distal small vessel occlusion, and venous arterialization of the distal venous bed might be a valuable surgical option. This study demonstrates the in-vivo microcirculatory effects of this type of intervention. Methods: Using intravital video microscopy, the authors studied the distal skeletal microcirculatory characteristics following venous arterialization of critical hindlimb ischemia in the rat. 25 Wistar rats underwent proximal ligation of the femoral arteries followed by venous arterialization carried out by anastomosing the saphenous vein to the femoral artery using microsurgery techniques. Microcirculatory hemodynamic conditions of the soleus muscle were observed under normal, ischemic, and arterialized conditions. Fluorescein-labeled red cells were used to measure red cell velocities (Vrbc) at the capillaries, and acridine orange injections used to stain endothelial cell nuclei to measure microcirculatory diameters, and leukocyte nuclei to measure leukocyte adhesion. Laser Doppler Perfusion (LDP) units at the distal limb were measured continuously throughout the procedure. Results: Proximal femoral arterial ligation resulted in drastic reductions in LDP and Vrbc. Following distal venous arterialization, LDP returned to an average of 41% of baseline. Vrbc returned to near baseline values in 70% of the capillaries. Flow at the capillary and venular system showed frequent reversals and great variations in velocities. Venules and venu-venular anastomoses diameters increased by 50%. There was immediate macromolecular tracer leakage and leukocyte activation was significantly increased in both ischemic and arterialized groups (15 cells vs 156 and 178 cells respectively). Conclusion: Venous arterialization may provide an improvement in microcirculatory velocities but is accompanied by microcirculatory injury and dysfunction in the acute phase. These results suggest that mechanisms besides microcirculatory hemodynamics play a role in the overall picture of clinical effectivity of the procedure. Key words: Retrograde venous arterialization, ischemic skeletal muscle