Background and aim of the study: Knowledge on long-term patient outcome after implantation with the Medtronic Stentless Freestyle bioprosthesis is incomplete due to a limited follow up. In the present study, microsimulation was used to extrapolate the available primary data and to calculate the life expectancy and lifetime risks of valve-related events after aortic valve replacement (AVR) with the Freestyle bioprosthesis.
Methods: Eleven-year follow up data from 725 patients (mean age 72 +/- 8 years; range: 36-92 years) who underwent AVR with a Medtronic Freestyle bio-prosthesis were used to calculate the hazards of structural valvular deterioration (SVD) and of other valve-related events. Age-dependent Weibull distributions were used to model SVD. These results were incorporated into a mathematical microsimulation model, which then calculated the long-term outcomes for patients of any given age and gender.
Results: The annual hazards for thromboembolism and endocarditis were 2.9% and 0.45% per patient-year, respectively. For example, for a 72-year-old male patient the median time to SVD was 20.0 (17.8-22.4) years. The life expectancy, reoperation-free life expectancy and event-free life expectancy of this patient was 10.4, 9.7, and 7.2 years, respectively. The patient had a higher life expectancy compared to age and gender-matched persons in the general population. His lifetime risk of reoperation due to SVD was 15%.
Conclusion: The Medtronic Stentless Freestyle bioprosthesis performs well and offers a low lifetime risk of reoperation for elderly patients requiring AVR. The performance of the valve and the selective patient population might explain the higher life expectancy compared to age and gender-matched persons in the general population.