Stenting pulmonary artery stenosis in an infant with tricuspid atresia: Approach via the foramen ovale and ventricular septal defect using a long flexible sheath

Stent implantation is now the preferred strategy for pulmonary artery stenosis complicating a congenital heart anomaly. The stent, mounted on a balloon catheter, is usually advanced through a long sheath on a stiff guidewire. Thus, a large sized (at least 9-F) long sheath must be placed at the target site to implant a stent in the pulmonary artery. However, it may be difficult to advance a rigid large sized long sheath to the target because of a complicated or tortuous route. A useful technique for stent deployment for such a lesion using a long flexible sheath is reported. A 2 year and 10-month-old boy with tricuspid atresia (TA), ventricular septal defect (VSD), and pulmonary stenosis developed severe left pulmonary artery stenosis with central pulmonary artery hypertension as a consequence of a previous left modified Blalock−Taussig shunt. He underwent a left modified Blalock−Taussig shunt at 3 months, and a central shunt at 9 months. The left modified Blalock−Taussig shunt was ligated because of excessive pulmonary blood flow after the central shunt (Fig. 1a). Subsequently he underwent a palliative right ventricular outflow tract reconstruction with ligation of the central shunt at 1 year and 7 months, because of hypoxia and severe stenosis of the shunt. The narrowest diameter of the stenosis, the proximal pulmonary artery, and the distal left pulmonary artery, measured 2.4, 5.2 and 7.0 mm, respectively. The pressure gradient across the stenosis was 34 mmHg. The catheter approach route via the foramen ovale and VSD, in which the catheter tip must be turned through 180 degrees in the ventricles, made the use of a long sheath extremely difficult. Balloon dilatation was first attempted at 3 years and 1 month and this proved unsuccessful in relieving the stenosis. (a) Left pulmonary angiogram showed left pulmonary stenosis associated with previous left modified Blalock−Taussig shunt. The narrowest diameter was 2.4 mm. (b) The stent was delivered through a patent foramen ovale and ventricular septal defect with a front loading technique using a long flexible sheath. (c) A pulmonary angiogram after stent implantation showed a well dilated stenosis with a diameter of 7.1 mm. Subsequently stent implantation was planned with a front loading technique using a long flexible sheath (Arrow Flex sheath 9-F, 65 cm; Arrow, Pennsylvania, USA) at 3 years and 10 months (Fig. 1b). At that time he weighed 9.3 kg. Under general anesthesia, a 5-F short sheath was placed in the left femoral vein and a 12-F short sheath in the right. The stenosis was crossed with a 6-F wedge balloon catheter from the right femoral vein via the foramen ovale and the VSD. An Amplatz extra stiff guidewire (0.035 inch, 260 cm; Cook, Bloomington, USA) was advanced through the catheter. With a front loading technique, a Palmaz P128 stent was mounted on a Power Flex balloon catheter (balloon diameter, 8 mm; length 2 cm, J & J Cordis; Roden, Netherlands) in the long sheath. Before inserting the long sheath, balloon, and stent assembly, a temporary pacing catheter was placed in the left ventricle from the contralateral groin, in case of critical bradycardia. During the first deployment, we encountered considerable resistance in turning the assembly through 180 degrees to reach the right ventricular outflow tract. Serious bradycardia of 70 beats per min with hypotension to 50 mmHg systole developed. Ventricular pacing was started and stabilized the blood pressure. We conclude that stretching of the atrium, mitral annulus, and ventricle caused the bradycardia and hypotension and subsequently advanced the assembly under continued pacing. The stent successfully dilated the lesion to 7.1 mm (Fig. 1c). No critical hypotension developed at that time and no mitral regurgitation was detected by color Doppler after stent implantation. The right to left lung flow ratio on perfusion scan improved to 1.04, having been 2.81 prior to stent implantation. In TA with VSD, the catheter must be turned through 360 degrees to enter the left pulmonary artery. An ordinary long sheath easily kinks while negotiating such a course in the small infant heart. Furthermore, it is difficult for a metal stent, such as the Palmaz type, to traverse such an acute curve. A front loading technique using a 9-F long flexible sheath and a short stent was chosen to overcome this problem. Vascular access with a 12-F short sheath makes the stent, balloon, and long sheath assembly easy to insert and facilitates repeat attempts. One of our concerns was bradycardia due to stretching of the atrium and mitral annulus while advancing such a large assembly by a complex route. We elected to use an Amplatz extra stiff guidewire that is slightly softer than a Amplatz super stiff guidewire, believing that it would provide sufficient support for the assembly without stretching the heart excessively. The use of temporary pacing increased the safety of the procedure. In conclusion, a front loading technique using a 9-F long sheath is useful to negotiate a complicated route for stent deployment even in small infants. We thank Dr Peter M. Olley, Professor of Pediatrics, University of Alberta, for his assistance with the manuscript.

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