The Genesis stent: A new low‐profile stent for use in infants, children, and adults with congenital heart disease

Abstract

Placement of intravascular stents that can reach adult size in infants and smaller children has been limited by the large profile and poor flexibility of currently available stents. In vitro and in vivo testing of the Genesis stent was performed to evaluate crimpability, predeployment flexibility, and radial strength. Comparisons were made to the Palmaz iliac and IntraStent (IS) LD stents. Nine physicians placed 30 Genesis stents in swine pulmonary and systemic arteries to evaluate stent deliverability/crimpability. Two swine were recovered and underwent a second catheterization 8 weeks later, where the stents (n = 8) were reexpanded to maximal size. Angiographic and intravascular ultrasound (IVUS) assessments were performed. In vitro testing revealed the Genesis stent to have superior crimpability, flexibility, and comparable radial strength to the Palmaz iliac stent, and superior crimpability and radial strength and comparable flexibility to the IS LD series. During in vivo testing, the physicians graded the Genesis stent superior to the Palmaz stent regarding crimpability and deliverability, and superior to the IS LD stent in regard to crimpability, and comparable to or superior in deliverability. In the chronic animals, the Genesis stent was expanded up to maximal diameter 8 weeks following implantation. Angiographic and IVUS revealed no fractures no in-stent restenosis. The Genesis stent can be easily delivered through smaller sheaths, which will facilitate their use in infants and smaller children with vascular stenosis.

Endovascular Stenting of Obstructed Right Ventricle–to–Pulmonary Artery Conduits

“…25,26 With respect to stent fracture, another concerning finding of this study is that Palmaz Genesis stents, which have replaced Palmaz stents in the product line and in our practice, had a significantly greater tendency than Palmaz stents to fracture when deployed in obstructed RV-PA conduits. Radial strength testing with application of full-length arealoading has shown Palmaz and Palmaz Genesis stents to have similar radial strength, 22 but the discrepancy between these in vitro data and our clinical experience suggests that radial strength testing by full-length area-load methods does not accurately simulate the stresses to which a stent is exposed in an RV-PA conduit.…”

“…In many cases, and most of those in which fractures were observed in our series, the obstructed portion of the conduit is immediately behind the anterior chest wall, and the stent is effectively compressed between the chest wall and the heart. Bench-testing of Palmaz and Genesis stents demonstrates relatively high radial strength, [22][23][24] but vascular stents are not necessarily suited to withstand the asymmetric, cyclic compressive stresses to which they are subject in the setting of conduit compression between the chest wall and the beating heart. Stents used in other locations exposed to compression or cyclic stress are also observed to fracture relatively often.…”

Fracture of Cardiovascular Stents in Patients With Congenital Heart Disease

“…An obvious comparison is between Palmaz Genesis and older generation Palmaz iliac and renal stents, which are all similarly fabricated from laser cut stainless steel tubes. The newer Palmaz Genesis stents, which have equivalent or superior radial strength to previous generations of Palmaz stents on bench testing, 34 seem to present different fracture susceptibility in vivo. The design of the Genesis stent incorporates S-shaped sigma hinges that link adjacent rings of cells, imparting flexibility during delivery and limiting shortening during expansion.…”

“…The design of the Genesis stent incorporates S-shaped sigma hinges that link adjacent rings of cells, imparting flexibility during delivery and limiting shortening during expansion. 34 However, these hinges seem to constitute a relatively weak link, and fracture of Genesis stents often occurs circumferentially through planes of sigma hinges (Figures 4 and 6; Movie IV in the online-only Data Supplement), either partially or completely. These points of weakness also seem prone to overloading axial compression or extension during stent re-expansion, which can also result in fractures.…”

“…[25][26][27][28][29] In children and adults with congenital heart disease (CHD), stents are used to treat many conditions, including obstruction of systemic and pulmonary arteries and veins, prosthetic conduits, valves, and shunts, and to enlarge, establish, or maintain communications between vessels or chambers of the heart. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] Most stents placed for CHD are used off-label, to treat conditions for which the stents were not developed, tested, or approved, and they are frequently implanted in previously operated sites with nonuniform material properties, and they may also be exposed to high cyclic mechanical stress. Because patients with CHD who have stents placed are usually children or young adults, the expected lifespan of the stent may be many decades.…”