(Adds researcher comments, background on congenital heart defects)
By Ransdell Pierson and Bill Berkrot
WASHINGTON, March 30 (Reuters) - A non-surgically implanted heart valve meant to delay open heart surgery in children with congenital heart defects worked well for all but a few patients during a year of follow-up observation, in line with favorable results seen in original clinical trials of the Medtronic Inc product.
The Melody transcatheter pulmonary valve was approved in 2010 under a U.S. humanitarian device exemption, which allowed it on the market as long as a follow-up study was conducted to assess the product's reliability and safety. The valve is guided to the heart by a catheter, a minimally invasive procedure.
In the study of patients who had been implanted with the valve there was no narrowing of the valve, or stenosis, after six months in some 96.7 percent of the 90 patients for whom data was available.
After a year, there was no narrowing, significant leakage or need for additional intervention in 94 percent of patients, researchers said on Sunday.
"The valves had excellent function during the first year, judged by no more than mild leakage and very few patients had narrowing of the valve," said Dr. Aimee Armstrong of the University of Michigan C.S. Mott Children's Hospital Cardiac Catheterization Laboratories, who was lead investigator for the follow-up study sponsored by Medtronic.
The mean age of patients in the trial was 20, with ages ranging from 5 to 45. The valve is made from a cow's jugular vein that is sewn into a metal stent, and then inserted into the patient's leg and advanced to the heart.
Within the first year of the study, eight adverse events were seen, including three cases of heart infections, two abnormal heart rhythms and one case each of bacterial infection, major stent fracture and blood clot in the lung.
Patients will continue to be followed for five years.
Results of the multi-center study were released at the annual scientific sessions of the American College of Cardiology in Washington.
Congenital heart defects are the most common type of birth defect in the United States, affecting an estimated 1 million adults and 800,000 children.
Some 40,000 babies with the defects are born each year in the United States. Many have no pulmonary valve, which carries blood from the heart's right ventricle to the lungs, or only a very small pulmonary valve.
Some patients receive a connecting tube, or conduit, early in life, to provide blood flow. The conduits, typically made from cadaver pulmonary valves, from pig valves or bioprosthetic materials, are implanted during open heart surgery and essentially bypass the missing or inadequate pulmonary valve.
But the conduits over time can become leaky and narrowed, putting stress on the right ventricle and preventing it from squeezing properly. As a result, patients can develop abnormal life-threatening heart rhythms and symptoms such as inability to exercise.
At that point, patients have traditionally required open heart surgery to replace the pulmonary valve. But such surgery, which requires cutting open the rib cage to get direct access to the heart, causes scar tissue that makes future surgery much more difficult.
Medtronic's Melody valve is meant to provide additional blood flow when conduits become faulty, and thereby delay the need for more open heart surgery.
"Every time you do open heart surgery, more scar tissue develops, with more potential damage to the heart" in subsequent surgery, said lead investigator Armstrong.
She said it was too early to determine just how long the Melody valve would last, or how long it would delay the need for more open heart surgery. But she said patients in other trials have had the Medtronic valve for five to seven years, with no need for surgery.
To date, over 6,000 patients have received the Melody valves, more than half of them children having congenital heart defects.
Melody was the world's first approved transcatheter valve, and such valves could help speed recovery times and spare great expense.
"This is an overnight procedure," Armstrong said. "Most patients go home the next day, whereas open heart surgery typically requires a week of hospitalization and patients then take off school or work a few weeks after that." (Reporting by Ransdell Pierson; Editing by Rosalind Russell and Eric Walsh)
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