Surgeons warn against use of Mitroflow valve in young patients

Children’s hospital physicians cautioned surgeons against implanting the Mitroflow bioprosthetic aortic valve in young patients who undergo aortic valve replacement and recommended vigilant surveillance of those who already have the device.

Writing in the July 1 issue of Circulation, Susan F. Saleeb, MD, of Boston Children’s Hospital, and colleagues described their experience and insights using current generation pericardial bioprosthesis devices in children and young adults. They launched a review after an autopsy of a 13-year-old girl who died of a gastrointestinal illness revealed a valve implanted 23 months earlier was severely degenerated. An echocardiogram seven months before her death showed only mild stenosis and decreased mobility of a valve leaflet.

That discrepancy raised a red flag, prompting them to review all records of patients younger than 30 years who received a bovine pericardial bioprosthetic valve between 2009 and 2013. The review included two types of valves, Mitroflow LXA (Sorin Group) and the Magna and Magna Ease (Edwards Lifesciences). They also put in place a protocol to evaluate the patients every six months by echocardiogram. They collected echo data through Jan. 20, 2014.

The final analysis included 27 patients, 15 with Mitroflow LXA and 12 Magna or Magna Ease valves. Patients who received the Mitroflow valve were smaller and younger. At a median 13.7 month follow-up, five Mitroflow patients had valves fail at 19 and 33 months of implantation. By comparison, none of the valves in the Magna/Magna Ease group had failed at three years.

Saleeb et al calculated that freedom from valve failure for the Mitroflow group was 100 percent, 53 percent and 18 percent at one year, two years and three years, respectively.

They noted that progression from mild to severe aortic stenosis occurred over a median of six months. Explanted valves showed severe stenosis and in three cases, valve leaflets were stiff with little or no mobility. “The leaflets were virtually fixed in a nearly closed (diastolic) position, leaving only a small effective valve orifice,” they wrote. “The valve leaflets were densely and diffusely calcified.”

Based on their results, the researchers recommended that the Mitroflow valve not be used in children and very young adults who undergo aortic valve replacement. Those already implanted with the device should be monitored closely.

They did not evaluate risk factors, they acknowledged, and because their study was retrospective and small, they could not determine if other valves might be prone to similar failure.

In an accompanying editorial, Robert D.B. Jaquiss, MD, of Children’s Hospital in Durham, N.C., pointed out the drawbacks in using devices in young patients that had been evaluated in clinical trials enrolling primarily middle-age and elderly adults. He added that the Mitroflow valve does not have antimineralization, as the Magna and Magna Ease devices do, which could lead to calcification and accelerate degeneration.

He seconded the authors’ position. “The version of the Mitroflow valve available in the United States should not be implanted in young adults in the future,” he wrote, and physicians with young patients already treated with the valve should begin enhanced surveillance immediately.