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Ten-Year Comparison of Pericardial Tissue Valves Versus Mechanical Prostheses for Aortic Valve Replacement in Patients Younger Than 60 Years of Age
Study Questions:
How did survival and freedom from valve-related morbid events compare in a propensity-matched comparison of patients <60 years of age who underwent Carpentier-Edwards pericardial versus bileaflet mechanical prosthetic aortic valve replacement (AVR)?
Methods:
From January 2000 to December 2009, overall survival, valve-related events, and echocardiographic measures of hemodynamics were analyzed in all patients younger than 60 years of age who underwent biologic AVR at a single University hospital in Berne, Switzerland. Patients who underwent AVR with a Perimount Carpentier-Edwards pericardial tissue valve (n = 103) were selected and compared with a propensity-matched group of 103 patients who underwent AVR using a mechanical bileaflet valve. Mean follow-up was 33 ± 24 months (range, 2-120), and the mean age at implantation was 50.6 ± 8.8 years (bioprosthesis, 55 ± 8.9 years; mechanical valve, 50 ± 8.6 years; p = 0.03).
Results:
Survival was significantly reduced in patients after biologic AVR (90.3% vs. 98%; p = 0.04). Freedom from all valve-related complications (bioprosthesis, 54.5%; mechanical valve, 51.6%; p = nonsignificant [NS]) and freedom from reoperation (bioprostheses, 100%; mechanical valve, 98%; p = NS) were comparable between groups. The average transvalvular mean (11.2 ± 4.2 mm Hg vs. 10.5 ± 6.0 mm Hg, p = 0.05) and peak (19.9 ± 6.7 mm Hg vs. 16.7 ± 8.0 mm Hg, p = 0.03) gradients were higher after biologic AVR. Regression of the left ventricular mass index was more pronounced after mechanical AVR (118.5 ± 24.9 g/m2 vs. 126.5 ± 38.5 g/m2; p = NS). Echocardiographic patient-prosthesis mismatch was greater at follow-up after biological AVR (0.876 ± 0.2 cm2/m2 vs. 1.11 ± 0.4 cm2/m2; p = 0.01). Oral anticoagulation was a protective factor for survival among the bioprosthetic valve patients (p = 0.02).
Conclusions:
The authors concluded that, in this limited cohort of patients younger than 60 years old, biologic AVR was associated with reduced mid-term survival compared with survival after mechanical AVR. The authors noted similar valve-related event rates in each group, and attributed better outcomes after mechanical AVR to better hemodynamics and/or a protective effect of warfarin.
Perspective:
It is no longer feasible to perform prospective randomized trials comparing tissue and mechanical valves. Absent such data, it remains problematic to tease out the relative risks of morbid and mortal events after bioprosthetic versus mechanical valve replacement. This study is a good attempt to address mortality at a single institution using relatively current-generation prostheses. However, although propensity matching included some important variables, others (including age and renal failure––both strong predictors of mortality after AVR) were not. As a result, dissimilar groups were compared (at a minimum, mechanical valve patients were younger), and the study might simply have uncovered preoperative biases about which valves were implanted in which patients. Based on these data, it is difficult to conclude that valve choice played a causative role in determining mortality.
Keywords: Bioprosthesis, Warfarin, Switzerland
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