Patients with thoracic aortic disease pose many challenges. Frequently, these patients are older and present with multiple comorbidities. Additionally, the posterior location of the descending thoracic aorta requires a large thoracotomy incision, with its own inherent morbidity.

The modern surgical treatment of thoracic aortic disease began in the 1950s, when successful treatment utilizing segmental resection and graft replacement was first reported by Swan, Lam, DeBakey, and Etheridge.^1-3 Soon thereafter, DeBakey and Cooley reported the first successful repair of an ascending aortic aneurysm using cardiopulmonary bypass.⁴ Cardiopulmonary bypass and commercially available tube grafts were the mainstays of our surgical armamentarium for the next 30 years. Improved diagnostic capabilities, surgical techniques, and perioperative care have resulted in improved outcomes, even as the risk profile has worsened.^5,6 In an effort to limit the morbidity of these operations,^7,8 endovascular techniques emerged as an attractive alternative. Originally devised for high-risk patients, and following on developments directed toward aneurysms of the abdominal aorta, thoracic endovascular stent-graft technology has rapidly evolved. Although originally intended for repair of atherosclerotic thoracic aortic aneurysms,^9–11 thoracic stent-graft applications have been expanded to the treatment of multiple pathologies, including acute and chronic aortic dissections, penetrating atherosclerotic aortic ulcers, and thoracic aortic trauma.^12-19 Results have steadily improved, and long-term durability has been encouraging; however, the necessity for long-term follow-up remains,^20-22 with obvious financial implications.

Endovascular stent-graft technology, initially targeting the abdominal aortic aneurysm, was introduced by Parodi.²³ Balloon-expandable stents, sewn inside the ends of a vascular tube graft, were placed within the aneurysmal aorta, excluding the aneurysm sac. Simultaneously, at Stanford University Medical Center, a collaborative effort between interventional radiologists and cardiovascular surgeons proved highly synergistic and resulted in a homemade thoracic stent graft.

Self-expanding Gianturco Z stents (Cook Company, Bloomington, IN) were fastened together and covered with a woven Dacron graft (Meadox-Boston Scientific, Natick, MA; Fig. 50-1), and then compressed into a 28-French introducer sheath. The first homemade thoracic graft was implanted in the descending thoracic aorta in 1992 after Institutional Review Board (IRB) approval was obtained. Subsequently, a high-risk trial was approved for patients with thoracic aortic aneurysms who were deemed nonsurgical candidates.²⁴ Thirteen such patients were treated utilizing stent grafts, customized-designed for each patient. Placement of these stents was successful in all patients, with complete thrombosis of the aneurysm sac reported in 12 of the 13 patients. At 1 year, there were no deaths, paraplegia, strokes, or distal embolization.

Feasibility having been established, IRB approval was obtained for a subsequent trial of 103 patients, 60% of whom were deemed unfit for conventional open surgical repair.²⁵ Using the same “homemade” first-generation stent graft, complete aneurysm thrombosis was achieved in 83% of patients. Thirty-day mortality was 9% and was significantly associated with a history of cerebral vascular accidents and myocardial infarctions. Major perioperative morbidities included paraplegia in three patients, cerebrovascular accidents in seven patients, and respiratory insufficiency in 12 patients. Actuarial survival was 81% at 1 year and 73% at 2 years. Given the high-risk nature of this patient population, these first-generation results were deemed satisfactory. It was, however, recognized that mortality and morbidity occurred frequently and that long-term follow-up was necessary to establish the long-term efficacy. Subsequently, in 2004, mid-term results were reported for these initial 103 patients treated with first-generation stent grafts.²⁶ Overall actuarial survival was dismal; 82, 49, and 27% at 1, 5, and 8 years, respectively. However, for potentially operable candidates, survival was 93 and 78% at 1 and 5 years, respectively, as contrasted to a 74 and 31% survival at 1 and 5 years, respectively, in those patients deemed inoperable. Late rupture in 11 patients reinforced the mandate for continued lifelong follow-up.

This technology was extended to the treatment of complicated acute type B aortic dissections, as reported by Dake and associates in the New England Journal of Medicine in 1999.²⁷ Again, utilizing these first-generation homemade devices, stent grafts were placed across the primary entry tear, successfully excluding false lumen perfusion. Distal malperfusion was corrected, and false lumen thrombosis within the chest occurred in 79% of patients. Early mortality was 16%, which largely reflected very late referral. Favorable clinical results persisted out to a mean follow-up of 13 months.

Homemade stent-graft devices persisted for another 10 years, as commercial development was slow to evolve. Homemade devices were made in 10, 15, and 20 cm lengths, with diameters from 23 to 36 mm. Two-centimeter proximal and distal landing zones were recommended, and stent grafts were oversized to approximately 10 to 15%. These grafts were then loaded into 28-French delivery sheaths, which were advanced into the descending thoracic aorta, usually through a femoral artery cutdown. In addition to small iliofemoral vessels, additional anatomic constraints of these early first-generation stent grafts, which precluded either delivery or secure fixation, included acute angulation of the distal arch, a severe sigmoid-like tortuosity through the diaphragmatic crura, and excessive mural thrombus.

The advent of this new stent-graft technology required a new terminology for endoleaks, which allowed the aneurysmal sac to remain pressurized. Type I endoleaks occur at the proximal (A) or distal (B) attachment sites and signify a failure to achieve a hemostatic seal at these implant sites. Type II endoleaks denote a communication between a branch vessel and the excluded aneurysm sac, and are commonly seen with back-bleeding intercostal vessels. Type III endoleaks occur at graft to graft junctions, and Type IV endoleaks are characterized by increase in aneurysm sac size in the absence of an identifiable endoleak, variously referred to as endotension.

In 2005 and 2006, commercially produced stent grafts became available. Initially, the Gore Excluder TAG system (W.L. Gore, Sunnyvale, CA) was approved (Fig. 50-2), followed shortly thereafter by the Medtronic Talent Graft (Medtronic, Sunrise, FL) and the Cook Zenith (Cook Company, Bloomington, IN). These second- and third-generation endoprostheses addressed many of the deficiencies of the early homemade devices. The delivery systems have become increasingly smaller in diameter and more flexible. The exoskeleton has to provide high column strength and ductility and be compression- and kink-resistant. Nitinol is used predominantly, covered by either Dacron or polytetrafluoroethylene (PTFE) graft material.

In January 2005, the phase II multicenter trial of the Gore Excluder TAG thoracic endoprosthesis was reported.²⁸ This multicenter, prospective, nonrandomized trial was conducted at 17 sites and compared the results of stent-graft repair of descending thoracic aortic aneurysms in 140 patients, with the results of open repair in 94 patients. Strict inclusion and exclusion criteria were defined in an attempt to ensure comparability of both groups. Follow-up computed tomography (CT) scans were obtained at 1, 6, 12, and 24 months. For stent-graft patients, operative blood loss, renal failure, paraplegia, and mortality rates were all significantly less than for the open repair group (Fig. 50-3). Interestingly, stroke rates were approximately equal in both groups. ICU stay and total hospital stay and time to return to normal activity were approximately 50% shorter for the stent-graft group than for those with open repair. Although stent-graft patients had reduced aneurysm-related mortality out to 2 years (3% vs 10%), interestingly, all-cause mortality was similar between groups at 2 years, similar to the results of recent randomized trials in abdominal aortic aneurysm stent grafts.

Approximately 50% of all thoracic aortic aneurysms are located in the descending aorta; these aneurysms commonly arise at the level of the left subclavian artery and are often atherosclerotic in nature.²⁹ The size–rupture correlation has been demonstrated through the natural history of these aneurysms, as reported by Clouse and associates, using the Olmstead County database, in which thoracic aortic aneurysms have an overall 5-year rupture risk of 30%.³⁰ The Mount Sinai group has identified clinical variables that predict the risk for rupture, including increasing age, presence of chronic obstructive pulmonary disease, maximal thoracic and abdominal aneurysm diameter, and presence of pain.³¹ The Yale Aortic Diseases Group has documented rupture and dissection of thoracic aortic aneurysms at a median diameter of 7.2 cm.⁶ The Yale Group also reported the mean rate of rupture or dissection as 2% per year for smaller aneurysms, 3% for aneurysms 5.0 to 5.9 cm, and 6.9% for aneurysms 6.0 cm and larger.³² Open surgical graft replacement has been the traditional mainstay of treatment for these patients, and mortality rates of 5 to 10 % have been reported from experienced centers.^33,34 Similarly, paraplegia rates have decreased to the 3 to 8% range, with increasing risk associated with increased extent of resection, emergency operation, and renal dysfunction. Utilization of distal circulatory support and cerebral spinal fluid drainage was protective.^35-38 However, in an ever-increasingly elderly population with multiple comorbidities, endovascular repair has become increasingly attractive, especially for patients with favorable anatomy.