Long-term results of the Mitroflow aortic pericardial bioprosthesis in over 800 patients: limited durability and mechanisms of dysfunction

OBJECTIVES: The Mitroflow aortic pericardial bioprosthesis was widely employed in the past. However, some authors have recently reported early structural valve deterioration (SVD) of the Mitroflow LA/LXA model. Thus, we reviewed our experience with the Mitroflow bioprosthesis and studied the risk factors for SVD and mortality. METHODS: Records of patients who underwent aortic valve replacement with a Mitroflow bioprosthesis between November 2005 and January 2015 were retrospectively evaluated with Kaplan-Meier, Cox-regression and multistate analysis. Only patients with a complete clinical follow-up were included in the study. Average follow-up was 45 months and ended on 1 April 2016. RESULTS: Between November 2005 and January 2015, among the 916 patients undergoing aortic valve replacement with the Mitroflow prosthesis at our Institution, the 832 (90.8%) patients with follow-up information were included into the study. Fifty-two (6.2%) patients developed SVD (stenosis, n = 38; regurgitation, n = 7; mixed, n = 7). Freedom from SVD was 95.4% and 67.9%, at 5 and 9 years, respectively, without differences after stratification according to the prosthesis model (P = 0.87) and prosthesis size (P = 0.70). At the multivariable analysis, increasing age was identified as a protective factor against SVD (hazard ratio = 0.94, P < 0.001). Twenty (38.4%) patients with SVD underwent redo aortic valve replacement. At 5 and 9 years, survival was 64.5% and 43.1%, repectively. According to the multistate analysis, the fraction of patients living with degenerated valves at 9 years was 10.0%; 7.1% died following degeneration. CONCLUSIONS: The LA/LXA Mitroflow model showed limited long-term durability. Degenerated prostheses showed more stenosis than regurgitation. Patient age played an important role in the development of SVD.