Vessel restenosis versus "streamlining".

Restenosis secondary to intimal hyperplasia within small diameter intravascular stents is a major problem in the adult population with atherosclerotic vascular disease. In contrast, most large series of stent implants in congenital lesions suggest that restenosis is rarely a problem. Schneider and colleagues, in this issue of Heart, point out that paediatric patients grow and that stents implanted in the paediatric population must be capable of being redilated to accommodate for the growth of the patient. Vessel growth occurs in proportion to the patient’s relative somatic growth rather than simply in relation to weight gain, and growth related relative stenosis of the appropriately stented vessel is unlikely until the patient’s body (and his vessels) have grown 30–50%. In a large series with medium to long term follow up at the Texas Children’s Hospital, excessive intimal hyperplasia within stents occurred only rarely. When it does occur, there is usually some abnormality of the tissues and/or the stent implant, and the intimal hyperplasia usually does not result in a stenosis or restenosis of the vessels. Intimal hyperplasia most frequently occurs in areas where there is abnormal wall unsupported by the stent (for example, in William’s syndrome); where there is elongation or “stretch” of the vessel being stented (for example, after an arterial switch with a Le Compte procedure); where there is external compression/collapse of the stent; or where an irregularly expanded stent creates significant variations in the diameter of the vessel lumen within, or in the area adjacent to, the stent. In these lesions, the intimal hyperplasia reduces the lumen within the stent only to the diameter of the adjacent narrowest vessel. Once the adjacent and/or stented vessels are enlarged to a uniform diameter with further dilation and additional stent implants, the stented areas do not restenose back to the smaller diameters after they are redilated.