Medtronic and Gore & Associates have designed stent graft systems for zone 2 deployment with a branch to the left subclavian artery (SCA). These systems are designed to obviate the need for surgical revascularization of the left SCA, with device implantation from femoral access and wire/catheter access to the SCA. With the Medtronic system, through-and-through wire access is obtained from brachial and femoral access, whereas the Gore system only requires femoral access. This wire is precannulated through the branch, which aids in device alignment and advancement/deployment of the branching graft.
The Gore Excluder thoracoabdominal branch endoprosthesis is an off-the-shelf four-branched modular stent graft system (). It uses a four inner-branched perivisceral aortic component. It has two downgoing branches for the mesenteric vessels and two upgoing branches for the renal arteries. The aortic devices are deployed, and then the renal arteries are selected using precannulated catheters from femoral access. Access is then obtained antegrade from brachial access to selectively catheterize and stent the mesenteric arteries through precannulated portals. The device is designed to be used with the Gore Viabahn endoprosthesis and Gore Viabahn BX endoprosthesis with balloon expandable technology (Gore & Associates). These stent grafts are flexible to improve performance in a variety of anatomy and the devices included the heparin-bonded antithrombotic surface coating, CBAS Heparin Surface. In-human deployments were first performed in Brazil in 2014, and therefore, clinical experience remains limited at this time. Gore & Associates is working toward initiation of an early feasibility study in the United States.
The Gore TAG thoracic branch endoprosthesis has a new branching stent graft designed to accommodate the significant motion forces that occur in the arch (). The device is currently being studied in the United States for a zone 0–2 deployment. As with the Gore Excluder thoracoabdominal branch device, this system uses a precannulated retrograde inner portal. The retrograde branch orientation has several advantages and disadvantages. The retrograde orientation of the cuff likely facilitates advancement of the branch grafts from femoral access and would allow for deployment of a more proximal cuff if needed. However, there are few clinical data describing the durability and flow dynamics of retrograde branches available at this time. Furthermore, a retrograde branch may be challenging in a very steeply angulated aortic arch. Gore & Associates has a similar design in an earlier phase of development for zone 0/1 deployment with initial human implantations completed this year in an early feasibility study in the US; data are not yet available for this construct.
To ensure good long-term results, careful selection of appropriate landing zones and device sizing was performed. In this case, a valve was present near the venous anastomosis. The GORE VIABAHN Endoprosthesis should be landed well before a valve, or if a sufficient landing zone with at least 1 cm of healthy vein prevents landing before the valve, the device should cross the valve completely. Landing immediately before a valve increases the likelihood of compromised patency. With respect to diameter selection, the GORE VIABAHN Endoprosthesis is sized to the venous outflow end of the graft to ensure sufficient wall apposition for anchoring and reducing the risk of migration. The recommendation is oversizing by 5% to 20%. Wall apposition to the vein at the outflow of the GORE VIABAHN Endoprosthesis is not required, and the device can be smaller in diameter than the outflow vein. A smaller device than the outflow vein allows for excellent flow through the device and better outcomes. In this case, an 8 mm x 10 cm GORE VIABAHN Endoprosthesis graft was selected and then placed across the outflow stenosis, which provided sufficient length to cover the outflow stenosis as well as extending to a landing zone that was not compromised by a valve. Postdilation was performed following successful device placement. A plug was pulled and macerated. An excellent thrill and bruit were restored to the access with excellent circulation to the hand.
Upon returning with graft thrombosis and outflow stenosis, a superior venacavogram, axillary venogram, subclavian venogram, shuntogram, and a selective brachial arteriogram were performed. Thrombectomy was performed with the AngioJet (Boston Scientific Corporation) device to clear the clot within the graft. Severe outflow stenosis of approximately 90% was noted and initially treated with balloon angioplasty using a 7 mm x 8 cm angioplasty balloon. The high-grade stenosis was refractory to this treatment, which persisted even after further balloon inflation of the lesion with an 8 mm x 4 cm angioplasty balloon. The results were suboptimal with rebounding of approximately 50% after use of the second angioplasty balloon. We identified that the stenosis on the graft vein anastomotic and perianastomotic area was going to be compromised. As a result, placement of a GORE® VIABAHN® Endoprosthesis was selected to prolong functionality of the AV graft circuit.