Bridge stents in the management of obstructive vascular lesions in children

Abstract

T most frequently used stents in the pediatric population to date are Palmaz stents. Although Palmaz stents are useful, several disadvantages, namely, the need for a large delivery sheath, balloon rupture, and stent displacement, exist. In addition, longitudinal rigidity of the stent makes it difficult to traverse tortuous course. To circumvent some of these problems, we used bridge stents. These are balloonexpandable, flexible biliary/peripheral stents manufactured by Medtronic AVE (Santa Rosa, California). The purpose of this presentation is to describe our experience with off-label use of these stents in an attempt to evaluate the feasibility, safety and effectiveness in the management of vascular obstructive lesions in children. • • • All patients who had bridge stents implanted for treatment of vascular obstructive lesions in children during a 9-month period ending July 2000 are included. There were 8 children with branch pulmonary artery stenosis (BPS), 2 with postoperative aortic recoarctation, and 1 with postsurgical superior vena caval (SVC) stenosis. The stent is made up of stainless steel (2 mm in length) sinusoidal elements connected together by laser fusion. The sinusoidal elements are designed to form elliptorectangular struts, and this geometry provides strength and resists failure under pressure. The dual-helical, laser-fusion pattern of the elements provides for longitudinal flexibility. During mounting of the stent on the balloon, an elegant stent retention mechanism is used by “pillows” created by a combination of heat and pressure so that the balloon material fills in the space between the struts of the stents along its entire length. The stents are manufactured in sizes 6 to 10 mm in diameter in 1-mm increments and with lengths of 28, 40, and 60 mm. There is minimal foreshortening at the time of stent expansion/deployment. After clinical, 2-dimensional and Doppler echocardiographic and/or quantitative pulmonary perfusion scan (for BPS cases), data indicated significant obstructive lesions, and cardiac catheterization was undertaken to confirm the diagnosis and to consider stent placement. Informed consent was obtained from parents for off-label use of the bridge stents. Conscious sedation was obtained with intramuscular injection of a sedative mixture (meperidine hydrochloride, promethazine hydrochloride, chlorpromazine) and intermittent intravenous doses of medazolam and fentanyl. Initially, peak pressure gradients across the stenotic site and selective biplane cineangiography to demonstrate the stenotic lesion were obtained. An arterial line was placed to monitor pressures and blood gas values during the procedure. Heparin 100 U/kg was administered intravenously. Activated clotting times were monitored and maintained between 200 and 250 seconds by administration of additional doses of heparin, as needed. Access was obtained percutaneously via the femoral vein (n 5 7), internal jugular vein (n 5 2), or femoral artery (n 5 2). With the aid of a multi A-2 catheter (Cordis, Miami, Florida) and a floppy-tipped Benston guidewire (Cook, Bloomington, Indiana), the stenotic lesion was crossed. The Benston guidewire was replaced with an 0.035-inch, extra-stiff, exchange-length Amplatz guidewire (Cook). An 8Fr long Blue Cook sheath (Cook) with a radiopaque marker at the tip was positioned distal to the site of obstruction in 7 patients. In the remaining patients, a short sheath (8Fr in 3 and 7Fr in 1) was used. The selected stent, premounted on a balloon catheter, was advanced over the guidewire but within the sheath and positioned across the site of obstruction. The tip of the sheath was withdrawn proximal to the site of obstruction and the balloon inflated, thus implanting the stent. One or more balloon inflations were performed to ensure apposition of the stent against vessel walls. Pressure pullback recordings across the stent and angiography, usually via a multitrack catheter (Braun, Bethlehem, Pennsylvania) were obtained. Three doses of cefazolin, 25 mg/kg, were administered at 6to 8-hour intervals. The heparin effect was not reversed. On the morning after, aspirin 5 to 10 mg/kg/day as a single daily dose was administered and continued for a 6-week period. Repeat pulmonary perfusion scan (in patients with BPS), chest roentgenogram, and Doppler studies were obtained on the morning after stent placement. Follow-up clinical, chest x-ray, and echo-Doppler evaluations were performed 1, 6, and 12 months after the procedure. Eight patients with BPS were aged 0.4 to 13 years (median 10) with weights ranging from 6.1 to 48.2 kg (median 25). The primary diagnoses were complex congenital heart disease with pulmonary atresia or severe stenosis in 7 patients. Six of these patients had total surgical correction, but had significant BPS. The seventh patient had a prior bidirectional Glenn procedure. The final patient had repair of a diaphragmatic From the Division of Pediatric Cardiology, Saint Louis University School of Medicine/Cardinal Glennon Children’s Hospital, St. Louis, Missouri. Dr. Rao’s address is: Division of Pediatric Cardiology, Saint Louis University School of Medicine, 1465 South Grand Boulevard, St. Louis, Missouri 63104-1095. E-mail: raops@slu.edu. Manuscript received March 1, 2001; revised manuscript received and accepted April 30, 2001.