Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Tiny Coil Saves Hearts

Pet Column for the week of April 7, 2003

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

An ingenious approach to fixing a congenital heart defect is being practiced at veterinary hospitals across the country. In time, this less invasive approach may replace surgical repair as the preferred method of fixing this defect, called patent ductus arteriosus.

Among the many miracles surrounding birth is the process of the newborn's lungs filling with air for the first time. While in the womb, an animal receives all of its oxygen from the mother, so its lungs are collapsed and non-functioning. The blood circulating in the fetus bypasses the lungs via a natural pathway called the "ductus arteriosus." At birth, this pathway closes and blood is pumped from the right side of the heart to the lungs, to pick up oxygen, then back through the left side of the heart to carry its load of oxygen to the rest of the body.

But sometimes, something goes wrong and the path fails to close, meaning that the blood does not adequately flow to the lungs. This results in less oxygenated blood flowing from the left side of the heart. In a few cases, the blood may move directly from the pulmonary artery to the aorta, which is a more serious problem because now un-oxygenated blood is being sent to the tissues and can cause oxygen deficits in some parts of the body. In dogs as well in people patent ductus arteriosus is a fairly common birth defect.

According to Dr. Mark Oyama, a veterinary cardiologist at the University of Illinois Veterinary Teaching Hospital in Urbana, most cases of patent ductus arteriosis are currently treated surgically. "Surgical repair involves approaching the heart from the side of the animal and making an incision between the ribs in order to reach the heart to repair the defect," he says.

A new, less invasive method of repairing this defect involves occlusion of the vessel with a tiny metal coil. "The embolization coil is loaded into a catheter," says Dr. Oyama. "The catheter is placed into the femoral artery in the leg and fed through the artery to the heart, where it is positioned inside the ductus arteriosus."

The coil is pulled taut while it is inside the catheter, but once it is released, it reforms to the coil shape. Tiny forceps inside the catheter can be used to position the coil before letting go of it. The goal is to lodge the coil inside the ductus arteriosus. Little fibers on the coil cause a blood clot to form, thus blocking the ductus arteriosus and, hopefully, repairing the defect.

"At the University of Illinois, we do a lot of ductus arteriosus repairs using these embolization coils. However, except for at university teaching hospitals, this procedure is not widely available," notes Dr. Oyama. "The main advantage of using these coils is that it is a much less invasive procedure and does not require opening the chest. For this reason, the coil is the primary way that this defect is corrected in children."

One risk of this procedure is that the coil may become dislodged if it is not positioned correctly or it is too small to fill the defective vessel. If the coil becomes dislodged in the pulmonary artery, it could reach the lungs. If this happens, the coil must be retrieved.

"This risk is the main reason that surgical repair is more reliable than the coil technique," says Dr. Oyama. "Over the next several years, if the success rate with the coil at teaching hospitals becomes comparable to the success rate of surgical repair, then using the coil could become the preferred method of repair."

If you have any questions regarding repair of a patent ductus arteriosus or questions regarding other congenital heart defects, please contact your local veterinarian.