Clinical Study of Thoracic Excluder Endoprosthesis to Treat Descending Thoracic Aortic Diseases

Thoracic aortic aneurysm, while relatively rare, is a potentially lethal disorder with a poor long-term prognosis if not treated. As the aortic diameter increases, wall tension becomes higher, leading to further expansion of the aneurysm. Consequently, this disease process is a "progressive and self propagating" phenomena, and the natural history of the disease is progressive expansion of the aneurysm with eventual rupture. Patients with descending thoracic aortic aneurysms frequently have concomitant major medical conditions, making them poor candidates for major surgical procedures. Concomitant conditions may include: hypertension, chronic obstructive pulmonary disease, congestive heart failure, and peripheral vascular disease, including abdominal aortic aneurysm, previous stroke and peripheral arterial occlusive disease. The accepted treatment for aneurysms deemed to warrant intervention is surgical resection and repair. Operative and post operative complications contributing to early mortality after surgical repair of descending thoracic aortic aneurysms include low cardiac output, pulmonary insufficiency, myocardial infarction, postoperative hemorrhage, pulmonary embolism and sepsis. In addition to mortality, two of the gravest complications of this surgical procedure, neurologic complications due to spinal cord ischemia, such as paraplegia and paraparesis, and renal failure or dysfunction, remain common. Dissections, another disease process of the descending thoracic aorta, are rare. Aortic dissections are thought to start with a tear or disruption of the intimal lining of the aorta, either due to medial degenerative diseases, trauma or rupture of an ulcerated intimal plaque. Blood at systemic arterial pressures invades the underlying medial layer of the aortic wall, dissecting the layers of the aortic wall, and forming a false lumen. The dissection then propagates for varying distances and in varying directions along the length of the aorta. As the false lumen increases in size, arterial flow to the true aortic lumen and to arteries arising from the aorta may be blocked or disrupted. Depending upon the location of the primary intimal tear and the direction of dissection propagation, various vital organs may loose arterial blood supply, and the aorta may rupture into the pericardial sac or pleural space, leading to cardiac tamponade or free pleural rupture. Blood flow from the false lumen may reenter the true lumen through another intimal tear, which may occur proximal or distal to the first, depending on the direction of dissection propagation. Medical therapy is the first line treatment for dissections of the descending thoracic aorta, and is aimed at reducing the mean, peak and diastolic recoil arterial pressure and the dP/dt while maintaining sufficient pressure to adequately perfuse all vital organs. Surgical intervention is warranted for patients with progression of dissection, impending rupture, refractory hypertension, a sizable localized false aneurysmal component, or continued pain. A device has been designed to treat disease processes of the descending thoracic aorta. The Thoracic EXCLUDER Endoprosthesis is a device that allows for primary endovascular repair of the descending thoracic aorta and is intended to be used as an intraluminal blood conduit. The Thoracic EXCLUDER Endoprosthesis is a flexible, self-expanding endoprosthesis that is constrained on the leading end of a delivery catheter. A separate balloon catheter, the Thoracic EXCLUDER Balloon Catheter, is used to smooth the endoprosthesis following implantation. Subjects will undergo an evaluation of the endoprosthesis, and will also be evaluated for device and procedure related adverse events that may have occurred during the follow-up period. Follow-up will be completed at 1, 3, 6, 12, 24, 36, 48, and 60 months. Subject evaluation at 1 and 3 months will include a complete Physical Examination and a CT with contrast enhancement. Subject evaluation at 6, 12, 24, 36, 48, and 60 months will also undergo a complete Physical Examination, a CT with contrast enhancement, and a Chest X-Ray (AP, Lateral, and 2 obliques).