Preliminary testing and evaluation of the renata minima stent, an infant stent capable of achieving adult dimensions.
Zahn EM, Abbott E, Tailor N, Sathanandam S, Armer D. Catheter Cardiovasc Interv. 2021 May 4. doi: 10.1002/ccd.29706. Online ahead of print. PMID: 33942962
Take Home Points:
- The Renata Minima Stent is a cobalt chromium, balloon-expandable stent that has diameter potential of 4-22mm.
- In a growing animal model, the vast majority of stents were implanted successfully and were subsequently successfully re-dilated with foreshortening noted with successively larger diameters
- This stent represents an important advancement in stent design to meet a critical need in congenital cardiac catheterization.
Commentary by Dr. Arash Salavitabar (Ann Arbor Michigan) section editor of Pediatric Interventional Cardiology Journal Watch:
The authors describe the Renata Minima Stent, which is a cobalt chromium, balloon-expandable stent designed for implantation at small diameters and with significant expansion potential, tested here in a growing animal model. The stent diameter ranges from 4-22mm, with all stents having an initial length of 17mm. The stent is designed with its own delivery system, which consists of an inner balloon and a braided “delivery sheath” designed to cover the stent for delivery and allows for hand angiograms during stent positioning, and is currently available with its custom delivery balloon in 6 or 8mm diameters for implantation. Importantly, this is a low profile system that has an outer diameter reportedly comparable to that of a 4-French sheath, and can be delivered over a 0.014” or 0.018” guide wire or via a 6-French sheath.
In this animal model, 21/22 (95%) stents were successfully implanted in 6 piglets (initial weight 4.6 +/- 0.5kg), with the one unsuccessful implant being delivered through an early delivery system prototype. The majority of stented sites were either in the aorta or branch pulmonary artery. Stents were implanted with an average balloon inflation pressure of 11.8 +/−2.1 atm, resulting in an implant diameter of 6.9 +/− 1.2 mm and stent length of 16.9 +/− 0.8 mm. Average stent recoil was 0.8 mm +/− 0.5 (9.8% +/− 6.2). Four piglets had subsequent catheterizations and redilations were performed in 17/22 total stents. Stents were successfully re-dilated at an average of 54 days post-implantation, at which time stent diameter increased by 54% +/− 25% (p < .001) with foreshortening to a final stent length of 16.1 +/−1.5 mm. Three piglets (mean weight 95kg +/- 13.1) with 11 total stents had re-catheterizations at 5 months post-implantation, with re-dilation performed on 8 of those stents. Stent dilation diameters represented a 61% +/− 28% increase from the prior procedure, or a 125% +/− 35% increase in diameter since stent implantation. Two stents were over-dilated with 18mm and 16mm balloons, respectively, with a foreshortening of 23% +/− 9% and average final stent length of
13.1 mm (+/−1.5). There were no complications, however a strut fracture was noted after re-dilation to 16mm in one aortic and one LPA stent.
Two piglets were sacrificed at 1 month for histopathology, which showed neointimal cell growth was present in varying degrees, fibromuscular tissue, and mild-to-moderate
strut-associated inflammation. In late histopathologic evaluation of a recently dilated LPA stent, irregular neointimal growth and vascular wall damage was identified.
These are promising early results for a new stent option that aims to solve a common and extremely important problem: stent implantation in the infant or child that will allow for lifelong expansion potential to match vessel and somatic growth. There are several aspects that will need to be further tested in animal models, such as treatment of truly stenotic vessels, followed by trials in humans in order to determine efficacy and safety. Nonetheless, this is a much needed advancement in congenital cardiac catheterization.