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Prosthetic valve type for patients undergoing aortic valve replacement: a decision analysis
N J Birkmeyer1, J D Birkmeyer, A N Tosteson
1Department of Surgery and the Center For the Evaluative Clinical Sciences, Dartmouth Medical School, Hanover, New Hampshire, USA. nancyj.birkmeyer@dartmouth.edu
Background:
In two large, randomized, clinical trials long-term survival after aortic valve replacement (AVR) was similar for patients receiving tissue and mechanical aortic heart valve prostheses. Higher bleeding rates among patients with mechanical valves, who must receive permanent oral anticoagulation to prevent thromboembolism, were offset by higher reoperation rates for valve degeneration among patients with tissue valves. Because the average age of patients undergoing AVR and clinical practices have changed considerably since the randomized clinical trials were conducted, we performed a decision analysis to reassess the optimal valve type for patients undergoing AVR.
Methods:
We used a Markov state-transition model to simulate the occurrence of valve-related events and life expectancy for patients undergoing AVR. Probabilities of clinical events and mortality were derived from the randomized clinical trials and large follow-up studies.
Results:
Although the two valve types were associated with similar life expectancy in 60-year-old patients (mean age of patients in the randomized clinical trials), tissue valves were associated with greater life expectancy than mechanical valves (10.7 versus 11.1 years) in 70-year-old patients (currently mean age of AVR patients). For 70-year-old patients, the effects of major bleeding complications (24%) with mechanical valves substantially outweighed those of reoperation for valve failure (12%) with tissue valves at 12 years. Of the clinical practice changes assessed, the recommended valve type was most sensitive to changes in bleeding rates with anticoagulation. However, bleeding rates would have to be 68% lower than those reported in the European randomized clinical trial to affect the recommended valve type for 70-year-old patients. Reoperation rates would have to be five times higher, and mortality rates at reoperation would have to be four times higher to affect the recommended valve type for 70-year-old patients.
Conclusions:
Although mechanical valves are preferred for AVR patients less than 60 years old, most patients currently undergoing AVR are elderly and would benefit more from tissue valves.