AKT Chau

Abstract

Vascular stenoses and hypoplasia in children are often associated with congenital heart disease or occur as a residual lesion or complications after surgical repair. Among these lesions, branch pulmonary artery stenoses are the commonest, other lesions include coarctation of aorta, stenosis of systemic veins after Fontan repairs, post-operative pulmonary venous stenosis, aortopulmonary collateral artery or shunt stenosis and post-operative conduit stenosis. They are usually associated with significant mortality or morbidity if untreated. Conventional surgical repair for these vascular stenoses may be difficult, carries a high operative risk or is associated with disappointing outcome. Some of the lesions may even be surgically inaccessible. Balloon angioplasties may be effective in relieving obstruction in some of these lesions. It can achieve successful dilation in about 60% of branch pulmonary arterial stenoses but the success rate may be lower in other lesions. Furthermore, the effects of balloon angioplasties in many lesions are often temporary and restenosis as a result of elastic recoil or subsequent scarring and fibrosis is common. Implantation of a stent provides a firm support and maintain patency of the vessels after balloon dilatation. Both balloon-expandable and self-expanding stents have been used to treat various vascular stenoses but available evidence suggests that the former is more suitable for use in children as it can be redilated to a higher diameter to keep pace with growth and is associated with fewer complications. The clinical application of stent implantation to treat various vascular stenoses and congenital heart diseases has been continuously widened since the late 1980s. It has replaced surgery as the treatment of choice in branch pulmonary arterial stenoses, post-surgical recoarctation of aorta that are unresponsive to balloon angioplasty, systemic venous obstruction and systemic venous baffle obstruction in Mustard or Senning operations. In native coarctation beyond young infancy, stenting is increasingly accepted as a primary treatment in adolescence and adults to avoid the higher surgical risks in this group of patients. In young children who do not respond to primary balloon angioplasty for native coarctation, stent implantation has also become an accepted treatment provided a stent that allows redilation to the adult aortic diameter is used. Stent implantation in conduit stenosis can prolong the life span of the conduit and delay the time of reoperation. In complex heart diseases where there is aortopulmonary shunt or aortopulmonary collateral artery stenoses, stent implantation serves as an effective alternative to surgical treatment. Stenting of the arterial duct has been increasingly incorporated into the management strategy of complex pulmonary atresias and hypoplastic left heart syndrome. Transcatheter approach using stents to complete the Fontan palliation may avoid multiple operations in patients with univentricular heart. Percutaneous pulmonary and aortic valve implantation to treat the respective valvar regurgitations are innovative new applications of stent that have gained initial success. Although the medium to long-term outcomes after stent implantation of most of the vascular stenoses are promising, restenosis caused by intimal hyperplasia and growth remains a long-term concern but it can be treated effectively and safely by stent redilation. New stent design is expected to overcome the limitations of the present stents and further widen its scope of application. Stent implantation is a new therapeutic modality that has added to the armamentarium of the paediatric cardiologists and cardiac surgeons in treating congenital heart disease.