Conformable Gore® TAG® Thoracic Endoprosthesis for the treatment of thoracic aortic aneurysms

Although relatively uncommon, descending thoracic aortic aneurysms are lethal, with a natural history of progressive dilatation, rupture and death. The traditional treatment of these aneurysms involves open thoracotomy and replacement of the aneurysmal aorta with a prosthetic graft. Although successful and durable, this treatment is potentially associated with significant morbidity and mortality, especially given the advanced age and frequent comorbidities of patients harboring these aneurysms [1]. Rates of spinal cord ischemia (SCI) as high as 13% and operative mortality of 10% or more are reported [2], although superior results are found in select centers of excellence, including rates of SCI of 2% [3] and operative mortality of 5% [4]. Other potential major complications include respiratory failure, myocardial infarction, renal failure and stroke. Given the notable mortality and complications associated with open-repair, endovascular approaches to the treatment of descending thoracic aortic aneurysms have been developed. This method is known as thoracic endovascular aortic repair (TEVAR). The procedure involves placement of a covered stent graft(s) through a peripheral access artery, usually in the groin, into the descending thoracic aorta over a guidewire under radiographic imaging guidance. The device is introduced in a collapsed state within a sheath or outer covering to reduce the entry profile. Once in position, the outer covering or sheath is retracted allowing the tubular stent graft to expand and seal against the wall of the aorta. This results in the exclusion of the aneurysmal portion of the aorta with the endograft(s) anchoring proximally and distally to more normal caliber aorta. This strategy reduces operative mortality and morbidity as it avoids open thoracotomy and clamping of the thoracic aorta. There are currently five US FDA-approved thoracic endografts, with the Gore TAG (WL Gore and Associates, AZ, USA) endograft the first to be introduced in 1997 as a means to repair descending thoracic aortic aneurysms via endovascular methods. After various modifications, including the removal of the longitudinal spines used for columnar support and reinforcement of the expanded polytetrafluoroethylene (ePTFE) material, the Gore TAG Thoracic Endoprosthesis was the first endovascular thoracic aortic stent graft approved for use by the FDA in the USA on 23 March 2005 (Figure 1). The device was further modified in 2011 with the introduction of the third-generation Conformable TAG (C-TAG; WL Gore and Associates) device (Figure 2). Modifications were made in the new C-TAG with the goals of improving device conformability in the aortic arch and tortuous aortas, treating narrower diameter and tapered aortas, as well as resisting device compression.