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While survival is a toss-up between bioprosthetic and mechanical mitral valves in middle age, other outcomes show clear advantages for one type over the other, a population-based study suggested.

Propensity-matched actuarial survival at 15 years came out similar between valve types in 50- to 69-year-olds (57.5% mechanical and 59.9% bioprosthetic, P=0.62), , of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues found.

"The lack of survival difference refocuses the emphasis in decision making on the relative risks of major complications, and also on quality of life," they wrote in the April 14 issue of the .

Those other outcomes at 15 years in New York's Statewide Planning and Research Cooperative System, to which all inpatient hospitalizations across the state are reported, included:

• 62% higher risk of stroke with mechanical prostheses (rate 14.0% versus 6.8%, P=0.01)
• 41% lower relative risk of reoperation with mechanical valves (rate 5.0% versus 11.1%, P=0.03)
• 50% higher risk of major bleeding events with mechanical prostheses (rate 14.9% versus 9.0%, P=0.03)

"Even though these findings suggest bioprosthetic mitral valve replacement may be a reasonable alternative to mechanical prosthetic valve replacement in patients aged 50 to 69 years, the 15-year follow-up was insufficient to fully assess lifetime risks, particularly of reoperation," the group cautioned.

"Quality-of-life surveys indicate that many patients view the distant possibility of reoperation as a reasonable trade-off for freedom from lifelong anticoagulation, reduced quality of life, and poorer perceived health status associated with mechanical prosthetic valves," they added.

Given these new data, they continued, "the incremental risks of stroke and bleeding associated with mechanical prosthetic valve replacement should also be a major consideration in any discussion of prosthesis choice."

Expert consensus guidelines from the American Heart Association and American College of Cardiology for valvular heart disease recommend mechanical prosthetic valves for patients under age 60, but are agnostic on type of valve for those 60 to 70 years old.

The reason for that recommendation in younger and middle-age adults has been their higher lifetime risk of reoperation due to accelerated bioprosthetic structural valve degeneration, Chikwe's group noted.

However, "the adverse effects of mitral valve reoperation in contemporary practice seems limited," they wrote. "The 30-day mortality after reoperation was 5.3% in this multicenter cohort, and experienced centers report even lower operative mortality and excellent functional outcomes."

Their findings fit the randomized trials but counter those of three single-center studies that had suggested a mortality advantage to mechanical mitral valves, which Chikwe's group attributed to selection bias.

Their analysis of the administrative dataset couldn't completely rule out selection bias either, but they used propensity matching for the 664 pairs of patients for 19 baseline characteristics.

The retrospective cohort included 3,433 patients ages 50 to 69 who got primary, isolated mitral valve replacement in New York state hospitals from 1997 through 2007. The median duration of follow-up was 8.2 years.

Other limitations included possible underestimation of major bleeding by excluding iatrogenic hemorrhage related to subsequent procedures from the definition, as well as follow-up that may have been too short to be representative of lifetime risks for the age group studied, because "the incidence of bioprosthetic valve degeneration accelerates with time."

The researchers had previously performed a similar analysis, with similar findings, by aortic valve type for middle-age individuals, leading them to conclude that bioprosthetic aortic valves "may be a reasonable choice in patients ages 50 to 69 years."

While the researchers stopped short of making the same recommendation for mitral valves, they did note the shift toward bioprosthetic mitral valve replacement in the database. From 1997 to 2012, use of tissue valves rose from 8% to 60% of all procedures (P<0.001).

From the American Heart Association:

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