The effects of a mechanical thrombolytic device on normal canine vein valves

PURPOSE: To determine if the Arrow-Trerotola Percutaneous Thrombolytic Devi ce (PTD) causes damage to normal vein valves. MATERIALS AND METHODS: Ten lateral saphenous veins in five dogs were studie d with descending venography with use of a wedge balloon catheter positione d above 48 valves (demonstrating 51 valves) before and after five antegrade passes each with an over-the-wire (0.025-inch), 6.5-F, 9-mm-diameter PTD. Vein diameters were 3.2-11.4 mm (mean, 5.9 mm). Contrast matter was injecte d at incremental rates from 3 to 15 mL/min during continuous pressure monit oring. Imaging was performed with digital subtraction angiography at a rate of 1 frame/sec. The time to valve reflux was determined by noting the fram e at which reflux was first seen through the valve. The time to reflux and pressure required to reflux were compared before and after the PTD passes. All vessels were explanted and evaluated histologically for presence or abs ence of endothelial loss, thrombus formation, inflammation, or valve degene ration. Four veins in two animals were studied with venography to determine the variability of the venographic method. These veins thrombosed during v enography and therefore served as positive pathologic controls. In two anim als, one vein was studied with venography and one was not studied to provid e pathologic controls. RESULTS: With use of two physiologic tests of valve function, 77% of valves had minimal or no damage as assessed by valve competency and 80% had minim al or no damage as demonstrated by the change in the pressures the valve ca n withstand before reflux. Twenty-six of 51 valves (51%) had no difference or later reflux after PTD use. Thirteen (26%) refluxed 1 second earlier aft er PTD use and 12 (23%) refluxed greater than or equal to2 seconds earlier (six at 2, four at 3, and two at 4). Four of the six valves with more than a 2-second difference in reflux times were in valves with diameters less th an 4.2 mm. All these vessels were smaller than 7 mm in diameter. Twenty-one of 48 valve levels (44%) had no difference or sustained higher pressures b efore reflux after PTD use. Seventeen (36%) had a pressure drop of <10 mm H g; five (10%) had drops of 12-24 mm Hg; and five (10%) had drops of more th an 40 mm Hg. There was a significant difference in endothelial loss, thromb us formation, and inflammation between experimental veins, the veins with t hrombus, the venography controls, and the normal vein controls. There was s ignificant difference only in terms of inflammation when the experimental g roup was compared to the thrombosis group. CONCLUSION: The antegrade use of the PTD across normal canine vein valves d oes not cause physiologically significant damage in valves 7 mm or larger i n diameter in this animal model.