Experimental evaluation of porcine-valved conduits processed with a calcium-retarding agent (T6).

The effectiveness of a water-soluble C-12 alkyl sulfate (T6) (U.S. Patent No. 4,323,358) in retarding bioprosthetic calcification was evaluated in 23 porcine-valved conduits (13 T6-treated conduits and 10 controls) implanted in young sheep between the right ventricle and the pulmonary trunk. The grafts were divided into three groups according to the period of function: Group I, less than 2 months; Group II, 2 to 4 months; and Group III, 5 to 7 months. In Group I (four T6 and four controls), endocarditis occurred in five cases. In Group II (three T6 and three controls), four conduits showed severe fibrous peel ingrowth. In Group III (six T6 and three controls), fibrous peel was the main feature in four conduits and calcium deposits occurred in the porcine aortic wall in all cases, with cusp involvement in two; in both T6-treated and control conduits, chemical analysis showed a much lower calcium content of the cusps (8.45 +/- 80 versus 2.95 +/- 1.52 mg/gm dry weight, respectively) than that reported in other animal or human explants. The grade of calcification in control and T6-treated conduits was equal on x-ray analysis, and no differences in calcification patterns were noted on electron microscopy. This experimental model shows a low degree of cusp calcification and no significant differences between T6-treated and control conduits. Peel formation markedly interferes with performance of the porcine-valved conduit. The results of this analysis indicate that valved conduits are not the optimum model for evaluating calcium-retardant agents in biological valves.