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New endograft technologies target EVAR
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Several new endografts awaiting FDA approval may soon offer interventionalists new tools for endovascular abdominal aortic aneurysm repair.
In a presentation given at the 2008 Vascular Annual Meeting in San Diego, Neal S. Cayne, MD, assistant professor of medicine at New York University Medical Center, brought attention to five different endovascular abdominal aortic stent grafts that are expected to improve on current graft technologies.
“Just as in the automobile industry when we progressed from a primitive T-car to a sports car, we are now progressing from our first-generation grafts to much more advanced grafts,” Cayne said.
The Anaconda stent graft, manufactured by Vascutek, is delivered by a 20-Fr. to 22-Fr. system, with the largest proximal graft size at 34 mm and the largest iliac graft at 23 mm. The graft also includes a magnetized wire that assists in catheterization of the contralateral limb, as well as proximal nitinol hooks that prevent the device from migrating. According to Cayne, a particularly unique feature of the Anaconda graft is the ability to reposition its proximal ring stents after deployment, allowing for accurate proximal deployment.
“Once it is deployed, it can be completely collapsed along with its hooks, repositioned and fully redeployed,” Cayne said.
The Aorfix device, manufactured by Lombard Inc., can be delivered with a 22-Fr. device. It has a maximum proximal graft size of 33 mm and a maximum iliac size of 22 mm. Like the Anaconda, the Aorfix graft has proximal hooks to anchor it in place. According to Cayne, the graft also has increased flexibility.
“This device is currently under investigation for treatment of very highly angulated infrarenal necks,” Cayne said. “The circumferential rings and the crumple zones between give this device its high level of flexibility.”
The Aptus graft, manufactured by Aptus Inc., is delivered by a smaller 16-Fr. delivery apparatus and has a proximal graft size of 32 mm and an iliac size of 22 mm. The device is placed using a two-step deployment, according to Cayne. Using the two-step deployment, the operator can deploy the endo staples and if not satisfied with the placement can pull back and redeploy. The Aptus graft also uses unique parts called endostaples, which not only help anchor the graft in place within irregular-shaped necks but can also assist in sealing the proximal ring within the vessel. When satisfied with the staple position, a second step fully delivers the staple.
“Another unique feature is the interlocking limbs,” Cayne said. “On both legs of the main body, there is an end-type stent which sticks out, and each limb is wrapped proximally with fabric that is actually captured into the stent and locks it in place.”
Medtronic’s Endurant stent graft, with a 36 mm maximum proximal size and 28 mm maximum iliac size, is one of the larger devices. It is deployed using a device that resembles older Medtronic delivery systems, with an 18-Fr. to 20-Fr. hydrophilic sheath that gives the operator the ability to control the positioning of the transrenal stent.
“It is one of the larger devices, and the device is fairly flexible due to shorter 5-mm M stents,” said Cayne. “This stent design has decreased columnar strength, so they added five pairs of fixation rings after deployment for improved accuracy in order to prevent migration.”
The new generation Zenith stent discussed, was manufactured by Cook Medical Inc. Information about the graft, according to Cayne, was harder to obtain than with the other grafts. The device is deployed using a 16-Fr. to 18-Fr. device with a hydrophilic sheath.
“The new generation Zenith has a more compressible Z-stent and contains a new type of material that was a secret, and they would not tell me what it is,” Cayne said. “The new device does not have a top cap.”
The new grafts, although not completely through their respective pipelines and still awaiting FDA approval, represent improvements on older designs, and all aim to improve the effectiveness of endovascular abdominal aortic aneurysm repair (EVAR).
“We are learning from our past imperfections of abdominal aortic aneurysm endografts, and the newer technology and devices continue to improve, specifically, to offer deliverability, flexibility and fixation,” Cayne said. “Although we are moving closer to the Lamborghini of EVAR, we are not quite there yet.” – by Eric Raible
For more information:
- Cayne N. New devices for EVAR: differences and similarities.