The effects of anticalcification treatments on bioprosthetic heart valves implanted in sheep

Several preimplantation processes have been shown to inhibit the calcification of pieces of porcine aortic valves and of bovine parietal pericardium implanted subcutaneously in rats. To investigate the effectiveness of these processes in modifying the calcification of bioprosthetic valves implanted in an intracardiac position, mitral and tricuspid valve replacements were performed in young sheep. Bioprosthetic valves treated with the following preimplantation processes were studied: 1) surfactants, including sodium dodecyl sulfate, polysorbate-80, Triton X-100 and N-lauryl sarcosine; 2) covalently bound aminohydroxypropane diphosphonic acid; 3) toluidine blue; and 4) incorporation of polyacrylamide into valvular tissues. Quantitative calcium analyses showed that only the surfactants substantially reduced calcification of bioprostheses implanted in intracardiac positions. This effect was evident only in porcine aortic valvular bioprostheses, and not in pericardial bioprostheses. Triton X-100 and N-lauryl sarcosine not only reduced calcification but also induced alterations that decreased the durability of the valves. Toluidine blue decreased calcification to a degree that was statistically significant but not biologically important, while polyacrylamide incorporation and diphosphonate binding increased calcification. Thus, data regarding anticalcification treatments obtained from subcutaneous implantation studies in small animal models should be interpreted cautiously and validated by studies with intracardiac valvular implantation in large animals.