Study compares mechanical and bioprosthetic valves in middle-age adults

A database analysis of published studies found that adults between 40 and 70 years old had similar survival rates whether they received mechanical or stented bioprosthetic valves for aortic valve replacement.

Although mechanical valves were associated with fewer reoperations, bioprosthetic valves were associated with fewer thromboembolic events and major bleeding events.

Lead researcher Paul G. Bannon, PhD, of the Baird Institute of Applied Heart and Lung Surgical Research in Australia, and colleagues published their results online in the Annals of Internal Medicine..

“This systematic review supports the use of bioprosthetic valves in patients younger than the current recommendation of 65 years,” they wrote.

When determining the choice of valve, the researchers noted that patients and clinicians must consider numerous prosthesis factors, including hemodynamics, biocompatibility, thrombogenicity, durability and risk of reoperation. They also must be aware of patient factors such as life expectancy, lifestyle and medication adherence.

This analysis included 13 studies that took place through September 2015 compared clinical outcomes between mechanical and stented bioprosthetic valves for aortic valve replacement in patients between 40 and 70 years old. In all, the studies had 4,287 patients who received a mechanical valve and 4,259 patients who received a bioprosthetic valve.

The groups were well balanced at baseline. The mean age was approximately 59, while 71 percent of patients were males, 39 percent underwent a concomitant CABG procedure and 28 percent had coronary artery disease.

After five, 10 and 15 years, there were no significant differences in survival, stroke or endocarditis, according the researchers. Only one study examined survival beyond 15 years. In that trial, survival at 20 years was 52.3 percent in the mechanical valve group and 65.5 percent in the bioprosthetic valve group, while survival at 25 years was 41.2 percent and 51.7 percent, respectively.

At five years, there was no significant difference between the groups in the freedom from thromboembolic events. However, the mechanical valve group was associated with a significantly lower freedom from thromboembolic event at 10 and 15 years. The studies defined a thromboembolic event as “any thromboembolus that occurred in the absence of infection after the immediate perioperative period.”

Meanwhile, the mechanical valve group was associated with a significantly lower freedom from major bleeding event at five, 10 and 15 years. The researchers defined a major bleeding event as “any episode of internal or external bleeding that causes mortality, hospitalization or the need for blood transfusion.”

In addition, at five, 10 and 15 years, the mechanical valve group had a significantly greater freedom from reoperation. However, the researchers noted that the studies reported reoperation across all ages and did not provide information on subgroups of ages.

The researchers noted a few limitations of their analysis, including that the studies they chose were observational trials (prospective or retrospective) and that most studies enrolled patients who underwent concomitant CABG, which they mentioned was a confounding factor of long-term outcomes after valve placement.

“In general, [mechanical valve] patients have an increased risk of major bleeding due to anticoagulation therapy, and [bioprosthetic valve] patients have an increased need for reoperation due to [structural valve deterioration],” the researchers wrote. “Choosing the optimal aortic valve prosthesis for middle-aged patients presents a particular challenge due to the important considerations of longer life expectancy and a potentially more active lifestyle compared with older patients. Additionally, the introduction of new prostheses and new surgical techniques (including ViV TAVI and minimal access approaches for surgical AVR), as well as the continued reporting of longer-term outcomes in comparative studies makes this a complex decision that must be reached with each patient individually.”