Morphological comparison of primary tissue failure (PTF) in porcine mitral and aortic bioprostheses in the same patient

Clinical and pathological studies have not clearly demonstrated whether primary tissue failure (PTF) in porcine bioprostheses occurs more often in the mitral than in the aortic position. We have studied morphological alterations in both positions in the same individual in 15 patients (14 mitroaortic and 1 mitroaortotricuspid) reoperated upon for PTF. Bioprostheses explanted were photographed, radiographed and observed in transmitted polarizing light. All lesions received a score on the basis of morphological criteria. The creep of the stent was measured. Calcification was slightly heavier and the degree of creep was significantly greater in the mitral position. Tears, infiltration and pannus growth did not differ between the two positions. According to our study, there is no conclusive demonstration that bioprostheses degenerate earlier and more extensively in the mitral than in the aortic position.