Experience with 2nd generation Aorfix Endovascular Stent Graft.
The Aorfix™ stent graft has been in clinical use for over two years and recently achieved a milestone in the product’s US trial, Pythagoras, when Dr Mark Fillinger implanted the 2nd generation Aorfix™ into a patient with an 80° neck angle. This was the first time that the 2nd generation Aorfix™ had been used in the US and is believed to be the first severely angled neck to have been treated in a stent graft clinical trial in the US. Dr Fillinger is the Principle Investigator for Pythagoras but his interest in Aorfix™ is wider than its well known success in angled necks. “When I first handled the Aorfix™, I was intrigued by the hybrid design approach. It had much of the flexibility of the Ancure device, which was useful on many occasions, but the ring stents and modular design help control the implant much better during deployment. The implant felt conformable and likely to handle irregular anatomies, conical necks and changes in morphology.” To date, Dr Fillinger has placed 4 Aorfix™ and has found positioning the mouth to be precise. The proximal end of the graft is controlled throughout its deployment by being attached to its delivery system by two thin, semiflexible rods. These stabilize the mouth during delivery and can be left attached to the graft throughout its deployment, detachment becoming necessary when the delivery system is removed. These rods are essential in preventing the graft from toppling or jumping down when it is deployed. Aorfix™ was the subject of the European Arbiter study where it achieved aneurysm shrinkage in 60% of cases at six months and 83% of cases at 2 years. The device integrity and fixation is maintained during sac shrinkage.
Stent Graft Design
The inherent flexibility of the Aorfix™ design enables it to move with the anatomy of the vessel and thus remain patent throughout. To date in the US, the Pythagoras study has four patients to have reached six month or more follow- up; two are Dr Fillingers and of these he says, “I was pleased to see volume reduction of 20% at six months in one case and 24% at 12 months in the other. I understand that fellow investigators’ patients have also shown shrinkage at six months. In terms of sac shrinkage, this equals the best devices available and I hope to see these early indicators confirmed at the end of the study.” Dr Fillinger is applying techniques he developed with previous stent grafts to the deployment of Aorfix™. “The most important thing with this graft is to start the deployment 30 or 40mm above the renals to get the orientation and symmetry of the implant right before we pull it down to the renal landing zone. Rotation of flexible delivery systems usually works best when they are being pulled slowly distally. "The techniques we learned from other systems also work with Aorfix™; narrow access vessels can be dilated with a large sheath and core, followed by gentle but continuous pressure on the delivery system itself. I sometimes find the Meier wire is helpful in tortuous necks because it has a long semi stiff tip which you can pull back into the delivery system. The Aorfix™ Gen 2 delivery system has a flexible core and this technique helps it to align itself in angled vessels." Precision deployment is aided by the rotating ratchet handle of the delivery system. Designed to deploy the mouth of the implant in 12 distinct clicks, the ratchet permits controlled, considered placement which is very different from ’pull and pray’ systems. Aorfix™ employs four pairs of hooks to provide active fixation of the proximal end. Lombard engineers achieved high levels of fixation with the hooks, avoiding the need for a suprarenal component. They found that suprarenal designs usually involved rigid components that crossed the renal arteries, limiting those implants’ ability to tolerate peri-renal angulation.
Peter Phillips, President of Lombard Medical in the US added, "To date we have implanted 17 devices in our US trial with very high accuracy and excellent technical success. We use M2S models and analyses for all of our planning and it is clear that good quality CTs reconstructed with standardized 3D modeling techniques aid our outcomes significantly. In Europe, Lombard now offers a planning service based on its in-house Terarecon system and I strongly recommend that clinicians work with our sizing experts to plan their cases with the detail these systems provide.”