ADVANCED MATERIALS & PROCESSES | MARCH 2025 34 Recent development of “high-purity” Nitinol provides excellent fatigue resistance for challenging anatomies with large bending radii and operating strains. Starlight Cardiovascular, founded in 2020 by Beverly Tang, has taken a portfolio approach to address unmet needs in CHD treatment[6]. The company is developing a Nitinol ductus arteriosus (DA) stent system and a percutaneous pulmonary flow restrictor as minimally invasive alternatives to traditional surgical approaches. The ductus arteriosus stent (Fig. 2) provides crucial blood flow to either the lungs or body in babies born with critical congenital heart defects and replaces an open-chest surgery on a neonate with a minimally invasive approach. The ductus arteriosus stent balances radial force and conformability in tortuous vessels in a 3.3Fr system for ductal-dependent pulmonary circulation and a 5Fr system for ductal- dependent systemic circulation. These benefits would not be achievable without the superelastic properties of Nitinol. The percutaneous pulmonary flow restrictor (Fig. 3) consists of a Nitinol frame covered with expanded poly- tetrafluoroethylene. The device is designed to prevent dangerous over-circulation to the lungs in babies with certain pulmonary-systemic communicating circulations. The current standard of care is an open-chest procedure on an infant wherein small bands are sewn to cinch down the pulmonary arteries externally. This banding procedure is notoriously difficult and frustrating, as the resultant hemodynamics are unknown until the chest is closed and the lungs are returned to physiologic pressures. In addition, pulmonary banding causes pulmonary artery stenosis that oftentimes must be repaired in a subsequent surgical procedure. Starlight’s percutaneous pulmonary flow restrictors allow for devices with a precise restriction size to be placed via a catheterization procedure and expanded over time to account for increased blood flow needs with the mission of addressing the significant unmet need for right-sized medical devices in pediatric cardiology. Their focus has been on creating devices that can accommodate the unique challenges of treating children with congenital heart defects and other cardiovascular conditions, taking into account the need for devices that can grow with young patients and navigate smaller, more delicate vessels. “We want to come alongside the families that are on a CHD journey and say, ‘We’ve made something specifically for your child, and not just what they need in this moment, but also what they need over the course of their life. We want to be the solution that adapts with you,’” says Armer. Renata Medical developed the Minima stent (Fig. 1) for use in the treatment of native or acquired pulmonary artery stenoses or coarctation of the aorta. Minima is the only FDA approved stent system for treating infant vascular stenosis today, and is designed to be re-expanded to adult sizes in the years ahead. Pediatric stents with oversizing capability must be designed to expand with patient growth while providing high radial strength, allowing for thinner strut designs while maintaining structural integrity, low profile, longitudinal strength, and radiopacity. Cobalt-chromium remains the material of choice over Nitinol due its ability to be expanded via balloon angioplasty. Minima can be implanted in children as young as a few days old (≥ 1.5 kg) and is designed to be periodically expanded as the child grows into adulthood. NITINOL STENT AND FLOW RESTRICTOR Despite its limitations, Nitinol remains valuable for pediatric stenting due to its flexibility and conformability to vessel anatomy, especially in tortuous vessels, while maintaining high resistance to external compression forces. 4 Fig. 1 — Minima is the only FDA approved stent system for treating infant vascular stenosis and is designed to re-expand to adult sizes as the child grows. Courtesy of Renata Medical. FEATURE Fig. 2 — Starlight’s ductus arteriosus stent is a Nitinol stent that balances radial force and conformability in the tortuous anatomy of babies. Courtesy of Starlight Cardiovascular.
RkJQdWJsaXNoZXIy MTYyMzk3NQ==