January 21st, 2014

Dangerous Rapid Calcification Observed In Pediatric Patients After Aortic Valve Replacement

Pediatric cardiac surgeons at Boston Children’s Hospital are warning the medical community about a potentially fatal problem in children and young adults who received a bioprosthetic valve manufactured by Sorin. The surgeons initially became concerned when a young, asymptomatic patient died suddenly after her valve underwent rapid calcification, only 7 months after a routine follow-up echocardiogram found no signs of blockage.

“Congenital aortic valve diseases are one of the more common heart defects that we see,” said Pedro J. del Nido, the chair of cardiac surgery at BCH. Surgeons prefer whenever possible to repair the native valve in the hope that by the time it needs replacement the children will be old enough to receive an adult valve.” Valve replacement is never ideal. Mechanical valves are highly durable but require lifelong anticoagulation. Bioprosthetic valves, which are made from animal tissue, don’t require anticoagulation but are less durable and eventually need to be replaced. When a repaired valve deteriorates, or the child is not a suitable candidate for repair, adult valves may be implanted. BCH performs some 60 to 80 aortic valve surgeries each year, said del Nido.

In recent years surgeons at BCH and elsewhere started using the Sorin Mitroflow valve, which is made from bovine tissue, in the aortic position. (In children the valve has primarily been used to replace the pulmonary valve. No excess problems have been associated with this usage.) Following the death last year of the patient, who received the Mitroflow in 2011, doctors at BCH began an intense surveillance of all 18 patients at their institution who had received the Mitroflow valve in the aortic position. They found 4 additional cases of rapid calcification (three patients had their valves replaced with a mechanical valve; the other is being watched closely).

“The rapid failures that we’re reporting have only been reported with the Mitroflow,” said del Nido. “We expect all bioprosthetic valves to fail eventually. The difference now is the speed of the deterioration, in 2 to 3 years instead of the 6 years that we would expect.” Typically, he said, patients are followed on a yearly basis. “But the speed of deterioration is so rapid that you won’t catch this problem early on.” BCH is now recommending that children with the Mitroflow valve be followed every 4 to 6 months so problems can be caught before an event occurs.

The American Society of Echocardiography forwarded a letter to its members from del Nido and James Lock, the chair of the cardiology department at BCH. The BCH doctors have also notified the FDA and the manufacturer of Mitroflow, the Sorin Group.

John Osborne, a cardiologist in Texas, first notified me about this news and provided the following perspective:

This is a pediatric/young adult population with congenital and genetic forms of valve disease that had aortic valve replacement with this particular bioprothetic valve. While calcification and resultant prosthetic valve dysfunction– especially bioprosthetic valve stenosis– is a known complication of bioprosthetic valves, particularly in the young, the time course and hyperacute onset of this complication is what is so unusual. This process of degeneration and resultant dysfunction of bioprosthetic valves is usually fairly slow occurring over years, or at most months, and is easily identified by echocardiography so that the valve can be electively replaced prior to critical failure. In addition, these patients usually have symptoms to trigger an evaluation of the valve.

What the esteemed pediatric cardiothoracic and cardiology groups at Boston Children’s Hospital describe is a highly unusual situation where the valves appear to be working normally, then suddenly (over weeks, apparently – the accompanying graph in the letter describes this well) the valves become abruptly calcified and stenotic while the patients have NO symptoms to indicate prosthetic valve dysfunction. This scenario has resulted in at least one death. I have never heard of a similar problem of hyperacute calcification and failure in bioprosthetic valves which makes this biologically interesting and very concerning for the physicians and their patients with the Mitroflow valve in the aortic position.


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