http://repub.eur.nl/res/aut/2540/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/35244/ 2007-09-01T00:00:00Z Objective: Numerous reports have been published documenting the results of aortic valve replacement. It is often not easy to translate these outcomes involving the condition of the valve into the actual consequences for the patient. We previously developed an alternative method to study outcome after aortic valve replacement that allows direct estimation of patient outcome after aortic valve replacement: microsimulation modeling. The goal of this article is to provide insight into microsimulation methodology and to give an overview of the advantages and disadvantages of simulation methods (in particular microsimulation) in comparison with standard methods of outcome analysis. Methods: By using a primary dataset containing 1847 patients and 14,429 patient-years, advantages and disadvantages of standard methods of outcome analysis are discussed, and the potential role of microsimulation is illustrated by means of a step-by-step explanation of building, testing, and using such a model. Results: Total life expectancy, event-free life expectancy, and reoperation-free life expectancy for a 65-year-old male patient were 10.6 years, 9.2 years, and 9.8 years, respectively. Lifetime risk of reoperation due to structural valve deterioration was 13.3%. Conclusions: Microsimulation is capable of providing accurate estimates of age-related life expectancy and lifetime risk of reoperation for patients who underwent aortic valve replacement with the Carpentier-Edwards supra-annular valve. It provides a useful tool to facilitate and optimize the choice for a specific heart valve prosthesis in a particular patient. http://repub.eur.nl/res/pub/7337/ 2004-09-09T00:00:00Z Aortic valve replacement (AVR) is a surgical procedure aimed at replacing a diseased aortic valve with a prosthetic device. The prognosis of a patient after AVR depends on many interrelated factors. The objective of this thesis was to further develop and utilize the microsimulation methodology to determine the prognosis of patients after AVR with mechanical valves and bioprostheses, which in turn could assist in the optimal choice of a valve prosthesis for a given patient. http://repub.eur.nl/res/pub/8309/ 2004-01-01T00:00:00Z BACKGROUND: Mechanical valves and bioprostheses are widely used for aortic valve replacement. Though previous randomised studies indicate that there is no important difference in outcome after implantation with either type of valve, knowledge of outcomes after aortic valve replacement is incomplete. OBJECTIVE: To predict age and sex specific outcomes of patients after aortic valve replacement with bileaflet mechanical valves and stented porcine bioprostheses, and to provide evidence based support for the choice of prosthesis. METHODS: Meta-analysis of published results of primary aortic valve replacement with bileaflet mechanical prostheses (nine reports, 4274 patients, and 25,726 patient-years) and stented porcine bioprostheses (13 reports, 9007 patients, and 54,151 patient-years) was used to estimate the annual risks of postoperative valve related events and their outcomes. These estimates were entered into a microsimulation model, which was employed to calculate age and sex specific outcomes after aortic valve replacement. RESULTS: Life expectancy (LE) and event-free life expectancy (EFLE) for a 65 year old man after implantation with a mechanical valve or a bioprosthesis were 10.4 and 10.7 years and 7.7 and 8.4 years, respectively. The lifetime risk of at least one valve related event for a mechanical valve was 48%, and for a bioprosthesis, 44%. For LE and EFLE, the age crossover point between the two valve types was 59 and 60 years, respectively. CONCLUSIONS: Meta-analysis based microsimulation provides insight into the long term outcome after aortic valve replacement and suggests that the currently recommended age threshold for implanting a bioprosthesis could be lowered further. http://repub.eur.nl/res/pub/9617/ 2001-01-01T00:00:00Z BACKGROUND: Bioprostheses are widely used as an aortic valve substitute, but knowledge about prognosis is still incomplete. The purpose of this study was to provide insight into the age-related life expectancy and actual risks of reoperation and valve-related events of patients after aortic valve replacement with a porcine bioprosthesis. METHODS AND RESULTS: We conducted a meta-analysis of 9 selected reports on stented porcine bioprostheses, including 5837 patients with a total follow-up of 31 874 patient-years. The annual rates of valve thrombosis, thromboembolism, hemorrhage, and nonstructural dysfunction were 0.03%, 0.87%, 0.38%, and 0.38%, respectively. The annual rate of endocarditis was estimated at 0.68% for >6 months of implantation and was 5 times as high during the first 6 months. Structural valve deterioration was described with a Weibull model that incorporated lower risks for older patients. These estimates were used to parameterize, calibrate, and validate a mathematical microsimulation model. The model was used to predict life expectancy and actual risks of reoperation and valve-related events after implantation for patients of different ages. For a 65-year-old male, these figures were 11.3 years, 28%, and 47%, respectively. CONCLUSIONS: The combination of meta-analysis with microsimulation enabled a detailed insight into the prognosis after aortic valve replacement with a bioprosthesis for patients of different ages. This information will be useful for patient counseling and clinical decision making. It also could serve as a baseline for the evaluation of newer valve types.