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Clinical Decisionmaking

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Tissue prostheses may be better than mechanical ones for elderly patients undergoing aortic valve replacement

With the declining incidence of rheumatic valve disease, aortic valve replacement (AVR) is now performed primarily for degenerative valve disease in increasingly older patients. Unlike younger people, elderly men and women who need an AVR would benefit more from tissue valves than the mechanical valves which are commonly used in elderly patients, according to a study supported by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00070).

Prior studies have shown that long-term survival after AVR is similar for patients receiving tissue and mechanical aortic heart valve prostheses. In these cases, the higher bleeding rates among patients with durable mechanical valves, who must receive permanent oral anticoagulation (blood thinners) to prevent blood clots (thromboembolism), were offset by higher reoperation rates for valve degeneration among patients with tissue valves.

However, these researchers found that for 70-year-old patients, currently the mean age of those undergoing AVR, the effects of major bleeding complications with mechanical valves (24 percent) substantially outweighed those of reoperation for tissue valve failure (12 percent) at 12 years. Lead author, Nancy J.O. Birkmeyer, Ph.D., of Dartmouth-Hitchcock Medical Center, and her colleagues used a model to simulate the occurrence of valve-related events and life expectancy for patients undergoing AVR. They derived the probabilities of clinical events and mortality from several randomized clinical trials and large followup studies.

The researchers found that both valve types were associated with similar life expectancy in 60-year-old patients (mean age of patients in the clinical trials), but that tissue valves were associated with greater life expectancy in 70-year-old patients (11.1 vs. 10.7 years). This was probably related to risks of anticoagulation-related bleeding that increase with age. Also, tissue valve failure, which typically occurs 10 to 15 years after valve implantation, may be of lesser concern for older patients, who have lower valve failure rates and shorter life expectancies.

For more details, see "Prosthetic valve type for patients undergoing aortic valve replacement: A decision analysis," by Dr. Birkmeyer, John D. Birkmeyer, M.D., Anna N.A. Tosteson, Sc.D., and others, in the December 2000 Annals of Thoracic Surgery 70, pp. 1946-1952.

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