Suggestions that Mitroflow, a surgically implanted heart valve sold by Sorin, is unsafe in patients under 30 and might have contributed to a child’s death prompted a 6% fall in the company’s stock yesterday.
Analysts have said that the failure is not significant for Sorin as the paediatric market for the device is worth less than $1m. But the extremely rapid failure of the valve – severe calcification appeared to have developed in less than seven months – coupled with earlier research concluding that the Mitroflow was suboptimal for adult patients too, could mean that its use in all ages falls dramatically.
Two surgeons at Boston Children’s Hospital wrote to the American College of Cardiology to warn that in spring 2013 an apparently asymptomatic girl who had received an aortic Mitroflow valve two years earlier died suddenly during a severe gastrointestinal illness. The valve was subsequently found to have been severely obstructed owing to “rigid calcification within normal-appearing leaflets as opposed to calcific nodules on the surface of the valve” – a finding that the doctors called “highly unusual”.
Calcification – deposits of calcium accumulating on the valve’s leaflets, impairing flexibility – usually occurs incrementally as a patient ages and is the most common cause of aortic stenosis in older patients. It is very rare in one so young, and it seems to have happened fast; an echocardiogram performed seven months before the child died indicated excellent valve function.
The hospital then checked all its patients under the age of 30 who had been implanted with a bioprosthetic valve in the aortic position, finding two more asymptomatic people with severely obstructed Mitroflow valves, “with the same unusual morphologic features” as the first patient. A fourth whose valve was implanted at the institution was found to have had it removed at a different hospital.
Boston Children’s Hospital is now assessing all its Mitroflow recipients aged under 30 with echocardiograms every four to six months.
Mitroflow has been on the US market since 2007 and has been sold in Europe for more than 30 years; why the problem has only come to light now is a mystery. Mathieu Chabert, an analyst at Bryan, Garnier & Co, estimated worldwide Mitroflow to be worth around €40m ($55m) in 2013 – 5.6% of the group’s sales.
Mitroflow’s US label warns that some patients, including those who are 55 years old or under, may experience accelerated calcification of bioprosthetic heart valves. Mr Chabert wrote that recent research mentioning accelerated calcification with Mitroflow in adults had not prevented Sorin from gaining market share in the US with this valve.
Nevertheless, use of Mitroflow in children will surely be severely curtailed by the warning, and it seems probable that use in adults will at least be dented. Sorin must hope that concern over Mitroflow does not cross over to its other valves.