Improved stents for pediatric applications

Abstract

Balloon expandable intravascular stents have become an integral therapeutic option offered to children and adults with congenital heart disease over the past decade. Initially, the stainless steel Palmaz stent was developed for the treatment of adult peripheral vascular disease but was quickly integrated into the interventional pediatric cardiologist's armamentarium to treat vascular obstructions resistant to conventional balloon angioplasty. Unfortunately, the use of this stent in tortuous and large diameter vessels uncovered certain design flaws, including sharp-edges, a rigid frame, and unacceptable shortening characteristics when ‘overexpanded’. To complicate matters, the single long delivery balloon catheter has proven to be more of a problem than initially recognized. The balloon inflates at each end initially, causing flaring of the traumatic sharp edges of the Palmaz stent that may contribute to balloon rupture and/or vessel trauma. In addition, the partially inflated balloon acts as a ‘floatation’ catheter causing stent movement and possible stent embolization. In order to understand the technical problems encountered and potentially offer solutions for appropriate stent technology specifically designed and tested for treating vascular obstructions associated with congenital heart disease, this article has been written. In this chapter, we discuss the recently FDA approved stainless steel IntraTherapeutics, Inc. IntraStent™ Double Strut™ and LD endoprostheses in treating infants, children and young adults with congenital heart disease. The investigational NuMED CP stent composed of 90% platinum and 10% iridium 0.013″ round wire is also discussed. The early clinical experience using both of the new stents are compared to the earlier use of the Palmaz stent. An in-depth discussion of a balloon delivery catheter (NuMED BIB) specifically designed to deliver any stent in vessels with diameters from 8 to 24 mm is made. Finally, future stent technology such as covered stents using ePTFE and polyurethane and the innovative NuMED Pulmonary Valved Stent composed of bovine jugular veins are also discussed. A challenge goes out to all who are involved with the transcatheter therapy of patients with congenital heart disease: to study, to improve, and to design appropriate intravascular stents so that we may more safely and effectively treat the myriad of challenges facing the interventional pediatric cardiologist of today.