Long-term safety of mechanical prosthesis in valve replacement age- and location-dependent
The long-term mortality benefit conferred by mechanical over biologic prosthesis in valve replacement appears to be age- and location-dependent, according to findings of a US-based retrospective study.
“[T]he relative mortality benefit that was associated with mechanical valves persisted until approximately 53 [and 68] years of age [in patients undergoing aortic- and mitral-valve replacement, respectively],” said the researchers.
Researchers analysed data of patients who underwent primary aortic- or mitral-valve replacement (n=9,942 and 15,503, respectively) using either a biologic or mechanical prosthesis at 142 hospitals in California, US, between 1996 and 2013. At baseline, recipients of biologic prosthesis were older and had more comorbidities than those who received mechanical prosthesis.
Median follow-up time was 5.0 and 8.2 years among patients who received biologic and mechanical prosthesis, respectively, during aortic-valve replacement, and 4.6 and 7.6 years, respectively, among those who underwent mitral-valve replacement.
There was an age-related effect of prosthesis type on mortality, whereby the use of a biologic prosthesis (vs a mechanical prosthesis) in aortic-valve replacement was associated with a higher mortality rate at 15 years among patients aged 45–54 years (30.6 percent vs 26.4 percent; hazard ratio [HR], 1.23, 95 percent confidence interval [CI], 1.02–1.48; p=0.03) but not among those aged 55–64 years (HR, 1.04; p=0.60). [N Engl J Med 2017;377:1847-1857]
Use of a biologic prosthesis was also associated with elevated mortality at 15 years among patients undergoing mitral-valve replacement compared with use of a mechanical prosthesis in patients aged 40–49 years (44.1 percent vs 27.1 percent; HR, 1.88, 95 percent CI, 1.35–2.63; p<0.001) and 50–69 years (50.0 percent vs 45.3 percent; HR, 1.16, 95 percent CI, 1.04–1.30; p=0.01), while mortality risk was comparable between valve type among patients aged 70–79 years.
There was a lower incidence of stroke among patients aged 45–54 years and a lower incidence of bleeding among patients aged 45–64 years who received a biologic compared with a mechanical prosthesis during aortic-valve replacement. In patients undergoing mitral-valve replacement, stroke incidence was also lower among biologic prosthesis recipients aged 50–69 years only, while the incidence of bleeding was lower among biologic prosthesis recipients aged 50–79 years. Strokes and bleeding were associated with elevated mortality risk.
Patients, particularly younger ones, who received a biologic prosthesis during either aortic- or mitral-valve replacement had a higher risk for re-operation than those who received mechanical prosthesis.
“The choice of prosthesis for valve replacement is often determined by balancing the risks of anticoagulation and re-operation, and reports of improved durability of biologic prostheses have led to a substantial increase in their use,” said the researchers, who highlighted the increase in use of biologic prostheses from 11.5 to 51.6 percent and from 16.8 to 53.7 percent for aortic- and mitral-valve replacement, respectively, between 1996 and 2013.
According to the researchers, the current practice guidelines do not differentiate between aortic- and mitral-valve prosthesis, and the recommendations were made based on small studies and the use of valves implanted decades ago, which are now obsolete.
“[Thus, these findings have the] potential to significantly impact the current national practice guidelines,” said senior author Professor Joseph Woo from the Stanford University School of Medicine, Stanford, California, US.
“[J]ust in terms of age, the older you are, the less likely that you will outlive the durability of a biological valve,” he said.
“Over the last 15 or 20 years around the world, there has been a dramatic shift in the increased use of bioprosthetic valves,” said Professor Michael Argenziano from Columbia University, New York, US, who was not involved in the study. “This is the first paper to provide solid evidence that maybe we have been moving too quickly away from the mechanical valve.”
The researchers acknowledged the potential for residual confounding and that the changes in treatment practice over time may have affected the findings.