Branched and fenestrated stent grafts for endovascular repair of thoracic aortic aneurysms

Abstract

Most thoracic aortic aneurysms affect the unbranched segment between the subclavian and celiac arteries, and they can be repaired without ischemic complications by using unbranched stent grafts. However, more complicated forms of repair are required when the aneurysm encroaches on the aortic arch or the visceral aorta. Alternative maneuvers for preservation of the branch artery flow include stenting of the branch artery, fenestration of the stent graft, branching of the stent graft, extra-anatomic bypass, or some combination of these. Secure attachment and hemostatic sealing are two basic prerequisites for successful endovascular aneurysm repair. Both require stable, coaxial implantation of a stent graft within nondilated segments of the aorta. Unfortunately, the nondilated segment (neck) between the aneurysm and the vital arteries at both ends of the descending thoracic aorta is often short, angulated, irregular, or conical. Some authors advocate lengthening the implantation site by covering the origins of the subclavian or celiac arteries. Although both are well collateralized, catastrophic ischemic complications can occur, especially when the left vertebral artery is dominant, the internal mammary artery is connected to a coronary artery, or collateral arteries to the anterior spine arise from arteries that are aneurysmal or occluded. Fenestration and branch artery stenting are helpful in the presence of a short angulated neck. Both help to improve the lie of the stent graft by allowing it to be inserted further into nondilated aorta. The effect on the length of the sealing zone is less predictable because, unless the aneurysm emerges from the opposite wall of the aorta, both branch artery stents and fenestrations may serve as routes for type I endoleak into the aneurysm. Aneurysms that involve the aortic arch or visceral aorta can be repaired by entirely endovascular means only if the stent graft has a branch for each branch of the aneurysmal aorta. The branch bridges the gap between the lumen of