Are stent-grafts that rely primarily on oversized proximal stents for fixation at the end of their product life cycle? Is oversizing as a fixation method for stent-grafts being replaced with active proximal fixation? Does the endo aortic repair method of the near future involve two steps: first endoluminal delivery of the graft and then active fixation and seal to the aortic wall?
The failure of stent-graft design in regards to proximal fixation and sealing has been well documented and changes in aneurysm and aorta morphology after exclusion have compromised the stent-graft integrity in many cases. However, a start-up company recently invested in a stent-graft and a fixation device that provides active transmural aortic fixation at the proximal edge of the stent-graft. The innovation: not fully relying on oversizing but instead applying active means of proximal fixation.
How does it work? After the placement of a modular stent-graft, helical shaped tackers (hernia mesh fixation comes to mind) are screwed in place at the proximal attachment site with a 16 F endoluminal applicator device that articulates. Currently there is a 29-mm and a 24.5-mm sized stent-graft available, made out of woven polyester graft and nitinol stents. The proximal stented part of the graft is 14-mm long and features diamond-shaped cells that are sewn to the inside of the proximal edge of the stent-graft.
In AAA patients with aneurysm that have at least 15 mm necks, the system may be used just below the renal arteries with the expectation that oversizing of the stented neck and approximation of the graft to the aortic wall might prevent leaks. The distal portion of the stent-graft of the body features a nitinol stent for receiving the modular iliac limbs. During deployment of the proximal stent, the main body of the stent-graft remains in the 14 F delivery catheter for better positioning. Once the main body is stented into place, an articulating catheters and 035-inch guidewires supports the delivery of an over-the-wire guide device with obturator is positioned within the proximal aneurysm neck of covered by the stent-graft. After removal of obturator and guidewire, the distal tip of the steerable guide device is directed toward the inside of the stent-graft. An additional applier device loaded with a tacker is inserted through the catheter port in the proximal control handle at the end of the steerable guide device.
Once the applicator device is in contact with the stented part of the graft an experienced operator might have some tactile feedback for the half way partial release of the tacker in order to leave the possibility for re-positioning in with more satisfactory result. Full deployment of the tacker is achieved through the second activation of the applicator device. The single load applicator requires re-intubation for the delivery of the second re-loaded tacker inserted in the applier. A minimum of four tackers are placed circumferentially in each stent-graft. After removal of the guide device the guidewire is re-inserted for the delivery of the modular contralateral extension stent-grafts.
At the remaining side the stent-graft body is then deployed completely with the help of the control knob on the handle of the stent-graft delivery system which is then removed. The .035-inch guidewire is used for the delivery of the remaining extension stent-graft, which is delivered in the same fashion as the contralateral extension stent-graft. Angioplasty for opening the lumen of the new stent-graft is often practiced at the proximal seal location of the stent-graft and the main stent-graft extension.
If the iliac and proximal contrast injections reveal the source of an endoleak another angioplasty needs to be performed, and additional tackers are placed in order to attempt a tighter application of the stent-graft to the aorta. Feasibility tests are under way in order to evaluate the effectiveness of the procedure.
Further – the future ain’t what it used to be.
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