Durability of the Hancock MO bioprosthesis compared with standard aortic valve bioprostheses. Discussion

To compare the durability of the Hancock modified orifice (Hancock MO, model 250 [H-MO]) valve with two other commonly used standard aortic valve bioprostheses, a cohort of 1,602 patients undergoing aortic valve replacement using porcine valves between 1971 and 1990 (excluding simultaneous mitral valve replacement) was analyzed retrospectively using Cox model multivariate techniques. Five hundred sixty-one patients received a composite H-MO valve, 652 received a standard Hancock model 242 (H) valve, and 389 received a Carpentier-Edwards model 2625 (C-E) valve. Mean age was 60 ± 15 years (±1 standard deviation) (71% male). Follow-up (10,247 patient-years) extended to 15 years and was 97% complete. The main focus of this study was bioprosthetic durability, using The American Association for Thoracic Surgery/The Society of Thoracic Surgeons guidelines to define structural valve deterioration (SVD). Multivariate analysis revealed that (younger) age (p < 10 -5 ), liver disease (p = 0.02), and 1981 to 1985 operative period (p = 0.012) were the only significant, independent predictors of SVD. In concordance with previous reports, the SVD freedom estimate was greater than 90% at 15 years for patients older than 70 years of age. Hepatic dysfunction had an adverse effect on SVD (estimated freedom from event at 10 years was 34 ± 17% [standard error of mean] versus 78 ± 2% for those without liver disease), but this affected only 3% of patients. Interestingly, one operative period (1981 to 1985) was associated with a slightly higher risk of SVD compared to the three other 5-year time windows. Valve type did not emerge as a significant risk factor for SVD. Actuarial freedom from SVD estimates were 56 ± 6% for H-MO at 14 years, 56 ± 4% for H at 14 years, and 54 ± 10% for C-E at 12 years (p = 0.47). Because of possible improved hemodynamics associated with smaller H-MO valves, the multivariate analysis was repeated according to valve size. Again, valve type did not emerge as a significant determinant of SVD. Furthermore, valve type was not an independent risk factor associated with any other valve-related fatal or morbid events except for postoperative thromboembolic complications (favoring the H-MO valves). In conclusion, no statistically significant or clinically important difference in durability or other valve-related complications was demonstrated between the H-MO valve and the two other standard bioprostheses examined. Accordingly, the choice of a porcine bioprosthesis should be based on other factors, such as hemodynamic performance, ease of implantation, cost, and surgeon's preference.