Evaluation of Efficacy and Safety of Valvulotomes in an “Ex-vivo” In-situ Bypass Model

Abstract

A critical step in the performance of in-situ bypass is to produce incompetence of the venous valves. Currently, there are several commercially available valvulotomes designed to fulfill this task. The purpose of the present work was to evaluate, in an ex-vivo system simulating an in-situ bypass, the efficiency of valve cutting and the degree of luminal damage produced by four of the most commonly used instruments (Reusable LeMaitre, Expandable LeMaitre, Gore Eze-Sit, and Mills). Cryopreserved cadaveric veins (2.5-6 mm diameter) were mounted in a perfusion chamber and submerged in Ringer's lactate. The same buffer containing 0.6% papaverine was infused at a pressure of 100 mm Hg through a catheter inserted into the proximal end of the vein. The valvulotome to be evaluated was introduced through the distal end of the vein, advanced beyond the most proximal valve and withdrawn at a rate similar to that used clinically through the full length of the vein. The vein was opened longitudinally and the efficacy of valve cutting (expressed as percent of individual valve cut) and presence of luminal damage were carefully evaluated by means of a dissecting microscope. Thirty-three valves in seven segments of veins (mean size 4.35 ± 0.86 mm) were tested with the Reusable LeMaitre valvulotome. The percent of valvular cutting was 29.9 ± 33.4. The Expandable LeMaitre valvulotome was tested in 22 valves contained in five segments (vein diameter 4.07 ± 1.04 mm) and the percent of valvular cutting was 89.2 ± 15.7. The Gore Eze-Sit valvulotome produced a 80.6 ± 25.5% of cutting in the 32 valves contained in the seven venous segments tested (vein diameter 3.67 ± 0.42 mm). The Mills valvulotome was tested in five segments of vein containing 20 valves and there was a 82.1 ± 24.0% of valve cutting after valvulotomy (diameter 3.67 ± 0.57 mm). Statistical analysis demonstrated a significant difference with less cutting (p < 0.0001) when the results of the Reusable LeMaitre valvulotome were compared against each of the other three valvulotomes. Luminal damage was detected in one instance after use of the Mills valvulotome. The Expandable LeMaitre, Gore Eze-Sit, and Mills valvulotomes demonstrated consistent efficacy in valve cutting, the Mills valvulotome producing injury to the wall in one occasion. The Reusable LeMaitre valvulotome gave significantly poorer results, most likely related to failure of engagement of the circular blade. Because of the presently demonstrated safety and efficacy, and avoidance of need for long skin incisions, the Expandable LeMaitre and Gore Eze-Sit are the most promising of the four tested valvulotomes.