Modification by the Hancock T6 process of calcification of bioprosthetic cardiac valves implanted in sheep.

The effectiveness of the T6 process (surfactant treatment) to decrease calcification of porcine aortic valvular (PAV) and bovine pericardial (BPV) bioprostheses was investigated. Morphologic and biochemical studies were made of standard and T6-treated PAVs and BPVs that had been implanted for a mean of 20 weeks in the tricuspid position in young sheep. Gross, radiographic, histologic and ultrastructural observations showed that the calcific deposits were less severe in T6-treated (n = 9) than in standard PAVs (n = 7), but were similar in severity in T6-treated (n = 6) and standard BPVs (n = 7). This was confirmed by results of quantitative analyses for calcium in half of each cusp of each explanted valve. Because these results showed large differences in standard deviations in the 4 groups of sheep, natural logarithmic and square-root transformations were used for statistical comparisons. The mean calcium content (milligrams of calcium per gram of dry tissue) of standard PAVs (111 +/- 53) was greater than that of T6-treated PAVs (11 +/- 3) (p = 0.0037). The calcium content of T6-treated PAVs was lower than that of T6-treated BPVs (96 +/- 26) (p = 0.031). However, the calcium content of standard BPVs (35 +/- 13) was not different from that of T6-treated BPVs or standard PAVs. Thus, under conditions of relatively short-term implantation in the sheep model, the T6 process is useful for decreasing the extent of calcification in PAVs, but not in BPVs.