Repair of Thoracoabdominal Aortic Aneurysms

Patients diagnosed with TAAA have a poor medical history and require surgical intervention to extend life. Several repair techniques have been developed, but each carry risk. Open repairs are durable but have substantial perioperative mortality and postoperative morbidity. Endovascular techniques are plagued by high procedural complexity and poor branch vessel patency. Parallel techniques may have poor seal and may be prone to endoleak. In contrast, the manifold approach has circumferential seal at the proximal end of the system. It has relatively simple case planning and it has virtually no ischemic time. Due to these advantages, the Investigator believes the novel proposed technique may overcome some of the current clinical risks with other approaches. Patients who participate in this study may benefit from having a less invasive procedure compared to open repair of their thoracoabdominal aortic aneurysm. The Investigator expects the amount of discomfort, total blood loss, recovery time, and overall hospital stay to be less than open repair. Many of the patients presenting with a thoracoabdominal aneurysm are not candidates for open repair due to existing comorbidities. With the progressive nature of the disease, these patients have limited options for medical intervention and are willing to assume a higher amount of risk. The Medtronic Valiant Thoracoabdominal Stent Graft System is made up of two main body components and makes use of several off-the-shelf FDA-approved stent graft components. The two custom main body grafts are the thoracic bifurcation and the visceral manifold. The thoracic bifurcation is deployed in the thoracic aorta and provides the proximal seal for the device. For a Type I or II thoracoabdominal aneurysm the proximal seal is in zone 3, for Type III and V the device seals in zone 4. The two limbs of the thoracic bifurcation allows for continued aortic flow while deploying the visceral segment. The visceral manifold is deployed within the larger 20 mm limb of the thoracic bifurcation to set the stage for the visceral debranching. The branches of the visceral manifold extend to the visceral vessel with the use of covered bridging stents and provide distal seal of the manifold. The smaller 16 mm limb of the thoracic bifurcation extends to the infrarenal segment to either seal in zone 9 for a Type I and V and in zone 10 for Type II and III. All other connections in the device make use of sizes that are modular and independent of patient anatomy. The Medtronic Valiant Thoracoabdominal Stent Graft works to bifurcate aortic flow upstream of the target visceral vessels. This bifurcation has a two-fold benefit. First it allows for aortic flow to be compartmentalized into a visceral segment and an infrarenal segment providing for uninterrupted flow to the visceral vessels as well as the infrarenal segment throughout the procedure. If any of the connections cannot be made or the patient status declines during the procedure, then it can be staged and the connections can be made at a later date. Second, the upstream bifurcation encourages more favorable flow conditions in the bridging stents and target vessels which may prevent target vessel occlusion. This is due to the fact that the bifurcations are upstream providing a sweeping transition into the renal arteries that is smooth providing for relatively laminar flow conditions. The design demonstrates that more central aortic flow is obtained with this design increasing flow rates in the visceral vessels to potentially increase target vessel patency. The device can be used as an off-the-shelf system, negating the need for lead times associated with custom-built devices. The critical sizing will need to be done with the proximal end of the thoracic bifurcation, distal landing zone in the aorta or iliac arteries, and the bridging stents. The proximal end of the thoracic bifurcation can be sized by choosing any of the available sizes of the Medtronic TAAA thoracic bifurcation stent grafts, and the sizes of the bridging stents can be manipulated by choosing any of the commercially available sizes of the Atrium iCast. The Atrium iCasts are added to the system in-vivo and connected with passive fixation which negates the need to size the main body components based on the target vessel sizes. All other connections in the device make use of sizes that are the same, independent of patient anatomy. The deployment of this device is also independent of device alignment. Angular alignment of the thoracic bifurcation and the visceral manifold has very little impact on the outcome of the case. Longitudinal alignment is more important, but a safety factor has been built-in by calling for the distal ends of the visceral manifold to be deployed above their target vessels by 1-2 cm. The longitudinal landing should be optimized so that the graft is not landed too low that the connection with the visceral vessels is challenging to make. Patients included in the study will undergo follow-up at one month, six months, twelve months and then annually for five years.