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Early Structural Valve Deterioration of Mitroflow Aortic Bioprosthesis: Mode, Incidence and Impact on Outcome in a Large Cohort of Patients
Study Questions:
What is the incidence, the mode, and the clinical impact of structural valve deterioration (SVD) in a large series of patients following Mitroflow aortic valve replacement (AVR)?
Methods:
Between 2002 and 2007, 617 consecutive patients (76.1 ± 6.3 years) underwent AVR with a Sorin Mitroflow prosthesis (models 12A and LX). SVD was defined using echocardiographic criteria: progression of aortic gradient ≥30 mm Hg associated with decreased effective orifice area ≤1 cm2, or intraprosthetic aortic regurgitation >2+/4+.
Results:
By echocardiography, 39 patients developed early SVD (1.66% per patient-year), mainly due to stenosis (n = 36). The mean interval to SVD was only 3.8 ± 1.4 years; and 5-year SVD-free survival was 91.6% (95% confidence interval [CI], 88.7-94.7) for the whole cohort, and 79.8% (71.2-89.4) and 94.0% (90.3-97.8) for 19 mm and 21 mm sizes, respectively. Among the 39 patients with SVD, 13 (33%) had accelerated SVD once the mean gradient exceeded 30 mm Hg. Valve-related death was 46.2% in this SVD subgroup; 5-year overall survival was 69.6% (65.7-73.9). In multivariable analysis, SVD was the strongest correlate of overall mortality (hazard ratio, 7.7; 95% CI, 4.4-13.6).
Conclusions:
Early SVD is frequent in Mitroflow bioprosthesis (models 12A and LX), especially for small sizes (19 mm and 21 mm), and is associated with reduced overall survival. An unpredictable accelerated pattern of SVD constitutes a life-threatening condition. The authors note that, in view of the large number of Mitroflow valves implanted worldwide, an epidemic of SVD and valve-related deaths can be anticipated, representing a major public health issue, especially in the elderly. The authors recommend close follow-up with yearly echocardiography after Mitroflow implantation, and discussion of urgent redo surgery for patients with severe SVD even if asymptomatic.
Perspective:
The Mitroflow AV bioprosthesis was designed to have favorable hemodynamics. However, structural valve deterioration has been a major issue with the device, with pericardial tissue tear and prosthetic regurgitation noted with an earlier model, and now evidence of prosthetic stenosis with recent and current models. Alternative bioprostheses with superior durability are available. For patients with a small-size Mitroflow device already implanted and with evidence of SVD, valve-in-valve transcatheter AV replacement (TAVR) will be problematic in light of the small internal diameter (15.4 mm) of the 19 mm Mitroflow, which will not accommodate currently available transcatheter devices.
Keywords: Public Health, Follow-Up Studies, Bioprosthesis, Constriction, Pathologic, Confidence Intervals, Heart Valve Prosthesis Implantation, Echocardiography, Aortic Valve Insufficiency
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