Heart Center: Intravascular Stent Placement
Branch pulmonary artery stenosis is a narrowing of the vessels that leave the heart and go to the lungs. This narrowing can be isolated to a particular area, can involve a long segment of the vessel, or can involve narrowing in multiple vessels. Branch pulmonary artery stenosis occurs in 2-3 percent of all patients with congenital heart disease, or 0.016 percent of the general population. It can occur as an isolated finding, in association with an inherited syndrome or chromosomal abnormality, or following surgery that involves the pulmonary arteries. The stenosis can result in increased right heart pressures, decreased pressure in the affected pulmonary artery, and decreased blood flow to the involved lung. The severity of the stenosis is based on the pressure difference, or gradient, before and after the narrowing. The higher the difference, the more severe the stenosis.
In the past, surgeons were asked to enlarge the pulmonary arteries by cutting them open and placing patches onto the vessels. This procedure was not very successful, however, unless the stenosis was very close to the main pulmonary artery and the stenosis was isolated. Today there is a nonsurgical option to open up the narrow pulmonary arteries called balloon angioplasty with intravascular stent placement. A stent is a tube made of stainless steel that looks like chicken wire. The stent is placed over a balloon and enlarged when the balloon is inflated. During the procedure, a catheter with a balloon on the end and a stent mounted on top of the balloon is advanced into the narrowed area through a blood vessel in the leg. Fluoroscopy (X-ray) guides the balloon and stent into the right position.
Once the catheter is in the correct place, the balloon is rapidly inflated and deflated to open the stent and dilate, or open, the narrowed area. When the catheter is removed, the stent remains in the vessel, enlarging the area. Pressures are measured and X-ray pictures are taken of the vessel before and after the procedure. This technique can be performed successfully on patients who have, and patients who have not, had prior surgery. Intravascular stent placement is performed most often in older patients because smaller children often need to have the stents re-dilated as they grow. After the procedure the patient will be admitted to the hospital for overnight observation and released the next morning. The patient will take antibiotics for one day to prevent infection and could take aspirin after the procedure for up to six months.
The results for intravascular stent placement for pulmonary artery stenosis vary. Success depends on the type and location of the narrowing, inflation pressure used to inflate the balloon and dilate the stent, and whether the stenosis is associated with a syndrome or chromosomal abnormality. Stent placement in response to stenosis associated with genetic syndromes or caused by previous shunts has a somewhat lower success rate. The immediate success rate, as determined by a 75 percent increase in the narrowed area, a 50 percent decrease in the pressure gradient, or a 25% increase in blood flow to the affected lung, is approximately 96 percent. The risk of death is less than 1 percent. In five years, 25-30 percent of the stents may require re-dilation.
A few complications can occur with these procedures, all less than 2 percent. These complications include femoral vein damage, pulmonary artery damage, stent mal-deployment, lung edema or fluid accumulation, bleeding, increased X-ray exposure time, and death. To combat these complications, the balloon size is carefully matched to the pulmonary vessel size, and heparin, a blood thinner, is given to prevent blood clot formation. Blood is ordered and is available for immediate use in case of bleeding.
Your cardiologist and Dr. Zellers will inform you more fully about this procedure on the morning of your child's catheterization. You will be able to ask questions and will be asked to sign a consent form. Your cardiologist will determine the need for further follow-up, which may include an echocardiogram the day after the procedure. A cardiac catheterization may be required in the future depending upon the echocardiography results.
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