Age thresholds for prophylactic replacement of Björk-Shiley convexo-concave heart valves. A clinical and economic evaluation.

Abstract

Björk-Shiley convexo-concave heart valves have an increased risk of mechanical failure. One might consider prophylactic rereplacement as a preventive measure to avert the disastrous consequences of these failures. We investigated the effect that prophylactic rereplacement has on survival of individual patients and on the medical costs. Quantitative estimates for the surgical risks of prophylactic replacement of Björk-Shiley valves, long-term survival, and the risk of outlet strut fracture were derived insofar as possible from a detailed analysis of a follow-up study conducted in The Netherlands, including 2303 patients with a mean follow-up of 6.6 years. On the basis of these estimates, we calculated life expectancy with and without prophylactic replacement. For the various valve types, age thresholds were determined below which rereplacement prolongs (discounted quality-adjusted) life expectancy. We also calculated the cost per year of life gained as a function of age. The age thresholds below which prophylactic rereplacement increases life expectancy (expressed in simple future years of life) for male patients without comorbidity, if the surgical mortality after rereplacement is equivalent to that of primary replacement, are 27, 48, 51, and 65 years for small and large 60 degrees and for small and large 70 degrees mitral valves, respectively. For aortic valves, these age thresholds lie somewhat higher: 39, 52, 56, and 76 years, respectively. Repeat analyses indicated that for women, all age thresholds lie about 1 or 2 years higher. These age thresholds decrease considerably if the surgical mortality after rereplacement is considered to be higher after prophylactic rereplacement than after primary replacement or if comorbidity is present. The costs per discounted and quality-adjusted year of life gained depend on type and position of the Björk-Shiley convexo-concave heart valve and rise steeply as the patient's age approaches the threshold for rereplacement. The results of the Dutch follow-up study allow guidance for prophylactic replacement of the Björk-Shiley convexo-concave valve on an individual basis. Rereplacement compares favorably with expectant management in some patient subgroups with both 60 degrees and 70 degrees valves. Age thresholds may serve as a first step in identifying patients in whom rereplacement might be beneficial.