Early Structural Valve Deterioration of the Mitroflow Aortic Bioprosthesis: Will the New Anticalcification Treatment Change Anything?

T here has been a trend toward more frequent use of biopros-thetic valves, especially in the young generations, over the last decade. 1 Freedom from warfa-rin use and restrictions on diet and activities make bioprosthetic valves more attractive and popular, and multiple reports have shown that choosing a bioprosthetic valve does not decrease survival despite the increased rate of reoperation. The Mitroflow aortic prosthesis (Sorin Group Inc) is one of the most frequently used bioprostheses, with >100 000 implanted worldwide. 5 The bovine pericardium is mounted externally around the stent, which maximizes the flow relative to the stent size. The valve is placed in the supra-annular position compared with the intra-annular position in some of the other bioprostheses. These characteristics allow superior valve hemodynamics in the Mitroflow aortic valve, especially in those with a small aortic annulus (19 and 21 mm) 6 ; therefore , the Mitroflow aortic valve is considered an ideal valve for patients with a small aortic root. The Achilles heel of the bioprosthetic valve is structural valve deterioration (SVD). Cusp tears and thickening, calcifi-cation, pannus formation, and thrombus lead to deterioration of the valve, 7 which is the leading reason for reoperation in bioprosthetic valves. The rate of SVD differs among ages; valves implanted in younger patients degenerate faster. For patients >65 years of age, the 10-year freedom from SVD in new pericardial valves is typically >90%. 8 In this issue of Circulation, Sénage et al 9 strike a note of warning against the use of the Mitroflow aortic valve. Some of the previous reports have shown 99% 5-year freedom from SVD in Mitroflow valve, 6,10 but in this report, the 5-year freedom from SVD was 91.6% and, when a 19-mm Mitroflow was used, 79.8%. The follow-up time was short (3.8±2.0 years), but the first SVD was observed only 14 months after implantation. The cumulative probability of SVD increased significantly from 0.8% at 2 years to 8.4% at 5 years. Most of this early SVD (92%) was caused by calcified prosthetic stenosis rather than a tear of the leaflet or regurgitation. A small-diameter prosthesis (19 and 21 mm) was used in 64.2% of the patients and was a significant risk factor for SVD in both univariate and multivariate analyses. This is a big concern because Mitroflow has been considered the ideal valve in patients with a small root, as mentioned earlier. This is not the first …