Thoracoabdominal Artery Stent Graft System Exploratory Study

Thoracoabdominal Aortic Aneurysms involve both thoracic and abdominal aortic arteries, as well as abdominal aortic aneurysms above the renal arteries. The treatment of TAAAs is complicated because the disease involves multiple visceral arteries. Traditional methods of treatment of TAAA include open surgery and hybrid surgery. The early postoperative mortality, as well as postoperative complications such as respiratory failure, renal failure, and other vital organ complications are concern for open surgery, which makes the benefit-risk ratio of traditional open surgery remains unsatisfactory. In addition, open surgery requires thoracoabdominal incision which will result in huge wound and the reconstruction of visceral artery is also complicated. Hybrid surgery, comprised of an initial open visceral debranching procedure followed by endovascular aneurysm exclusion, is another treatment option. Although hybrid surgery can reduce the huge wound caused by thoracotomy, it does not seem to result in lower complication rates at early and midterm follow up.

With the rapid development of endovascular treatment technology, endovascular therapy is also applied in the treatment of TAAA, and gradually becomes one of the main treatment method. Especially for patients with high surgical risk because of comorbidities, an endovascular solution may be preferable. Total endovascular aneurysm repair (t-EVAR) without debranching surgery does not require thoracotomy and laparotomy and could improve the outcomes of these patients. t-EVAR includes fenestrated EVAR (f-EVAR), multi-branched EVAR (b-EVAR), and physician-modified fenestration endograft (PMFG). Compared with open surgery and hybrid surgery, endovascular therapy has the following advantages: 1) minimally invasive surgery, avoiding thoracic and abdominal incision; 2) avoiding aorta occlusion during the operation so that reduce various visceral ischemia complications; 3) reducing intraoperative blood loss and hospital stay; 4) reducing spinal cord complications.

The TAAA stent graft system used for endovascular treatment generally consists of a stent graft and a delivery system. Stent graft, also known as artificial stent-type vascular graft, is generally composed of tubular covered and metal wire braided stent. The stent can be compressed into the sheath which delivers the stent to the lesion site of TAAA, and then is released from the sheath. The stent opens by its own expansion force to separate the blood from the lesion site, so as to achieve the treatment purpose. Custom made stents need to be designed and manufactured according to the patient's aortic characteristics, and the 6-8 week waiting period limits its use in patients who show precursors to rupture or who have already ruptured. Currently commercially available off-the-shelf multibranched stent grafts for TAAA include Zenith t-Branch stent (Cook), E-nside TAAA Multibranch Stent Graft System (Jotec) and GORE® EXCLUDER® Thoracoabdominal Branch Endoprosthesis (Gore \& Associates). A critical issue with these multibranched stent grafts is the limited device specification and suboptimal anatomical feasibility for TAAA patients, therefore, improvements to the device profile, configuration and size optimization are needed. In the current context, Lifetech have developed a new TAAA stent graft system, Thoracoabdominal Artery Stent Graft System, which is a mixed branch design with two inner branches for the visceral arteries and two outer branches for the bilateral renal arteries. It is an off-the-shelf multibranched endograft and there is no need to waste time on customisation. The variations in the main body diameter, length and branch size, introducing diversified configurations that accommodate more anatomic conditions. Two inner branches are integrated with preloaded guidewires to facilitate visceral artery cannulation and reduce the procedure time. The semi-release design allows the stent position to be adjusted during the release process, making the stent positioning more accurate and less difficult.