Modes of failure in explanted mitroflow pericardial valves.

BACKGROUND: Bioprosthetic heart valves are a treatment option for patients with significant valvular disease. We present the first morphologic analysis of a series of explanted Mitroflow pericardial valves (model A12) and discuss their modes of failure. METHODS: Between 2001 and 2010, 12 Mitroflow (A12) valves (Sorin Group Inc, Vancouver, Canada) were examined, grossly and microscopically, for postimplantation changes. Cusp tears and thickening, calcification (at radiography), pannus formation, inflammation, and thrombus deposition were noted. Microscopically, tissue degeneration including the presence of calcification, pannus formation, thrombus, collagen disruption, fluid insudation, inflammatory cells, and microorganisms were looked for. Causes for dysfunction were then identified. RESULTS: There were 12 patients with a mean age of 73.0 ± 5.3 years at implantation. Duration of implantation ranged from 0.25 to 7 years (mean = 2.9 ± 2.5 years). Five valves were explanted for infective endocarditis or thrombotic vegetations. Primary structural deterioration was observed in 7 of 12 (58%) valves; characterized by para-stent post cusp tears (42%) and moderate to severe calcification (50%). Most valves showed cusp thickening and collagen disruption at the stent post and pannus. CONCLUSIONS: Structural valve deterioration was observed in 100% of the Mitroflow pericardial valves that had been in place for more than 2 years. The high rate of para-stent post cusp tears, calcification, and tissue degeneration suggests a link to the design, likely associated with mechanical stress, in addition to abrasion with the cross-sutures and Dacron fabric at the stent posts.