In Reply Dr Head and colleagues outline 3 misconceptions on which a preference for mechanical valves in younger patients has historically been based: (1) the mortality risk attributed to bioprosthetic valve degeneration; (2) the effect of reoperation; and (3) the durability of mechanical valves.
In support of the association between mechanical valves and survival benefit in younger patients, Head and colleagues cite a retrospective comparison1 in which confounding variables, including cancer, liver disease, and coagulopathy, were not controlled. The difficulty of adjusting for key confounders is inherent in observational studies and is why the survival benefit attributed to mechanical valves may in fact result from the established practice of implanting bioprosthetic valves in patients with shorter life expectancy.
Chikwe J, Egorova NN, Adams DH. Age Cutoffs for Bioprosthetic vs Mechanical Aortic Valve Replacement—Reply. JAMA. 2015;313(5):523-524. doi:10.1001/jama.2014.17231