Blood vessel plug - amplatzer ductal occluder, performs well in trial

Aug 5 2004

In the largest and longest trial yet of a device called the Amplatzer ductal occluder, a duct that shunts blood flow away from the lungs during fetal development but sometimes fails to close after birth, was successfully closed in almost all patients, according to a new study in the Aug. 4, 2004, issue of the Journal of the American College of Cardiology.

“With the widespread introduction of this device, patent ductus arteriosus (PDA) closure can be attempted and performed successfully in the vast majority of patients with PDAs, obviating the need for surgery,” said Robert H. Pass, MD at Columbia University in New York.

Because the lungs are not used during fetal development, a duct between the descending aorta and the pulmonary artery short-circuits blood flow. In some people, this duct fails to completely close after birth. People who have PDA are at increased risk for bacterial infections, heart failure, pulmonary vascular disease, and pulmonary hypertension.

Although surgeons can close the duct, researchers seeking less traumatic alternatives have developed devices that can be threaded through catheters and then placed within the duct to close it. These devices include coils around which blood clots, thus closing the duct. However, these coils can be difficult to use and may not work to close larger openings. The Amplatzer ductal occluder is a wire mesh made of nitinol, a superelastic alloy of nickel and titanium that opens into a bell-shape to fill the duct.

“This device was effective in closure of over 99 percent of all PDAs in which it was implanted at one year follow-up. When one considers that over 70 of these patients had PDAs that were over 4 mm and therefore “large” in diameter, it is clear that the device offers a significant advantage over the coil technique,” Dr. Pass said.

Previous trials with the Amplatzer device involved relatively small numbers of patients. By contrast, this study enrolled 484 patients at 25 U.S. centers from September 1999 to June 2002. Patients who appeared to be good candidates for receiving this device were referred by cardiologists at the participating centers, in consultation with the investigators. On average, the participants were younger than 2 years old; however, they ranged in age from just 2 months to over 70 years. About 9 percent of the patients did not have a device implanted, either because the duct opening was too small or because of elevated resistance in the pulmonary blood vessels. The Amplatzer device was successfully implanted in 435 of the remaining 439 participants. There was no control group.

“There were rare complications in this project. There were two device embolizations, one of which required surgical retrieval of the device. Two patients had left pulmonary artery obstruction to a moderate degree. This will be something that requires further study,” Dr. Pass said. A device embolization means that the device became dislodged from the duct.

This study did not directly compare the Amplatzer device to alternative devices or surgery, which has become a relatively uncommon option

“A clear limitation of the study is the fact that it was not randomized. Patients were chosen by the institution's individual referring cardiologists in consultation with the participating investigators. There is no direct comparison between this device and other devices, but in truth, to our knowledge, there is no patent ductus arteriosus device presently available that has as broad an indication as the Amplatzer device,” Dr. Pass said.

Phillip Moore, MD, at the University of California in San Francisco, who was not connected to this research team, noted that PDA is one of the most common congenital heart defects affecting children. He added that although surgical repair of open ducts has been done for more than 50 years, catheter devices that allow for less traumatic treatment have been available only since the 1990s.

“This is the first multicenter trial in the United States looking at a device that’s specifically designed for closure of the ductus arteriosus,” Dr. Moore said. “This data has allowed for approval and generalized use of the device for closure of PDAs in the United States.”

Although this study did not directly compare the device to other approaches, Dr. Moore noted the relatively small number of cases that occur each year would make the cost and duration of that sort of randomized controlled trial difficult to justify.

“In the context of where they are, it was probably as good a trial as they could do to look at the usefulness of this particular device, as well as its risks and problems,” Dr. Moore said.

Ziyad Hijazi, MD, a member of the research team at the University of Chicago, is also a paid consultant to AGA Medical, the manufacturer of the Amplatzer PDA duct occluder device.

The American College of Cardiology, a 29,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.