Low-profile porcine bioprosthesis (Liotta): pathologic findings and mode of failure in the long-term

BACKGROUND AND AIMS OF THE STUDY: The Liotta low profile porcine bioprosthesis (LBP) was designed in order to minimize complications due to excessive protrusion of the stent prongs in the left ventricle. MATERIALS AND METHODS: From April 1984 to November 1993, 25 LBP surgical explants were available for pathology study, which included gross and X-ray evaluations. Reoperation was performed after a mean period of 95 +/- 25 months (range 46 to 143 months), in five males and 20 females (mean age at implantation 51.1 +/- 11.4 years). RESULTS: The cause of failure was stenosis due to cusp stiffness caused by dystrophic calcification in one and incompetence in 24 LBPs. In only one case was incompetence ascribable to endocarditis; in the remaining 23 the mechanism of regurgitation was due to commissural tearing (21 LBPs), commissural dehiscence (one LBP) and both tears and dehiscence (one LBP). Overall, 28 commissural tears were observed: 20 involved the right coronary cusp, eight the left coronary cusp, and none the non-coronary cusp. The anterior commissure was most frequently involved by tears (n = 17) followed by the right posterior (n = 9) and the left posterior (n = 2). Tears were calcium-related in all but two cases. Calcific deposits were observed in each explant, involving a total of 62 commissural attachments, 17 cusp bodies and five right muscular shelves. CONCLUSION: In conclusion, valve regurgitation is the usual mode of LBP failure in the mitral position; commissural tearing of the right coronary cusp was the most common cause of valve regurgitation, and occurred even in the presence of pin-point calcification. These pathologic findings seem to confirm that low profile design, which implies bulging of the right coronary cusp, entails the risk of increased stress at the commissures, accelerated calcification and tearing.