Mechanical Valves Beat Bioprostheses in Younger Patients

Reed Miller

February 04, 2011

February 4, 2011 (San Diego, California) — Younger aortic-valve-replacement recipients are more likely to survive another 10 years with a mechanical valve than a bioprosthesis, data from a small series in Switzerland suggest.

"More and more patients come to surgery already knowing and telling us what valve they want. Because of the quality of life, most of them prefer the bioprosthesis, because they don't want to take anticoagulation drugs," Dr Alberto Weber (University of Bern, Switzerland) told heartwire . "But we weren't sure we were doing it right. So we needed to look into our data."

Weber and colleagues tracked overall survival, valve-related adverse events, and left ventricular regression in 101 consecutive patients under the age of 60 who received a biological aortic-valve replacement (Carpentier-Edwards pericardial valve, Edwards Lifesciences). Their results were compared with a propensity-matched group of 91 patients who received a mechanical aortic valve (ATS, St Jude). Total follow-up was 1420 patient-years, an average of 20.7 months. Weber presented the results of the study at the Society of Thoracic Surgeons (STS) 2011 Annual Meeting.

The 10-year survival rate was significantly lower in the patients with the bioprosthetic valve than those with the mechanical valve (89.1% vs 96.7%, p<0.05). Freedom from all valve-related complications was statistically similar, 54.5% for the bioprosthesis group and 52.6% for the mechanical-valve group. Freedom from reoperations was 99% in both groups.

The average aortic mean pressure gradient was higher in the bioprosthetic valve group (11.2 mm Hg vs 10.5 mm Hg, p=0.05), as was the peak pressure gradient (19.9 mm Hg vs 16.7 mm Hg, p=0.03). Regression of the left ventricular mass index was also higher after mechanical-valve replacement than after bioprosthetic-valve replacement, but the difference was not significant.

Commenting on the study at the STS meeting, Dr Tomislav Mihaljevic (Cleveland Clinic, OH) pointed out that some previous studies have shown that mechanical-valve patients have better survival odds than bioprosthetic recipients because the bioprosthetic valves required more reoperations. But those reoperations tended to be close to 10 years after the implant, while in this study, the survival curves appeared to diverge early and the freedom from operation was similar between the two groups. That suggests that the hemodynamic performance of the bioprosthesis was not the main reason for the difference in the survival, Mihaljevic suggested. "I wonder if there could be some patient-related factors that contributed to the early, but substantial, increased mortality in patients who received a bioprosthesis."

Weber responded that since it was not a randomized trial, it is still possible that there was some unknown variable that made the two groups of patients different, but his group carefully looked for potential confounders, so this is not likely the explanation. The more likely explanation is that the mechanical valves worked better over the long run. "The survival of the bioprosthetic valve group is very good and not bad compared with the literature. What is astonishing are the really excellent results of the mechanical valves in this patient group. We had only three patients die out of 101, with quite a high risk. This is good news."

Weber told heartwire that with the advent of transcatheter valve systems, it is possible to put a new valve inside a failed bioprosthesis. But he argued that that possibility is not justification for using bioprosthetic valves in patients under 60. "We're talking about very young patients here. This new 'valve-in-valve valve' isn't going to last for good, so we would be facing, in these patients, two or three or four more reoperations. That's not a solution."

The availability of newer anticoagulation drugs that are easier to manage in the outpatient setting, such as dabigatran , may make patients more amenable to mechanical valves. "It's definitely worth a try to see how these new anticoagulants are going to perform with mechanical valves," Weber said. "It may signify a small revival of mechanical valves, because, hemodynamically, they are better than the bioprosthetic valves."

Weber and Mihaljevic reported no conflicts of interest.