work best for localized descending thoracic aneurysms, and are a logical extension of the extensive experience with infrarenal abdominal aortic aneurysms.

Thoracoabdominal aneurysms are significantly more dangerous, with repair resulting in published mortalities of 10-50% and incidence of paraplegia 7-25%. The location of these aneurysms and their proximity to and involvement of the spinal artery of Adamkiewicz and visceral vessels make them particularly treacherous (Fig. 7.16). The repair of such an aneurysm requires a thoracoabdominal incision. The patient is placed in the lateral decubitus position with the pelvis corkscrewed to gain access to the abdomen and groins. A low thoracic approach (usually the ninth interspace) is utilized, although if the aneurysm arises proxi-mally near the left subclavian, it may be necessary to perform a separate thorac-otomy in the fourth interspace to achieve exposure for the proximal anastomosis. The thoracoabdominal incision is extended to the midline of the abdomen and the diaphragm is entered along its periphery.

A retroperitoneal approach is used and the spleen, kidney and left colon are mobilized anteriorly and to the right to expose the aorta. Left atrial to femoral artery bypass is established. The aorta is cross-clamped proximal to the aneurysm and distally at a level above the visceral vessels (Figs. 7.17a-e). This permits continued perfusion of visceral and spinal vessels via the left atrial to femoral bypass circuit and decreases the chance of paraplegia. When the proximal anastomosis has been performed, the proximal clamp is taken off with the graft clamped to check the proximal anastomosis. The distal clamp above the visceral vessels is then

Fig. 7.20. Elephant trunk procedure. (a) The graft is inverted upon itself retrogradely into the arch graft. The distal elephant trunk portion is then pushed back down the descending thoracic aorta. Alternatively, the future arch graft is invaginated distally into the trunk and then extended out into the arch.

Fig. 7.20b. For distal elephant trunk insertion, the future trunk is inverted retrogradedly into the descending aortic graft, then pulled downstream just prior to completing the distal anastomosis.

removed after the left atrial femoral bypass circuit has been shut off. The visceral vessels are then re-implanted, usually with a celiac, superior mesenteric and right renal artery pedicle, and with the left renal as another pedicle. The cross-clamp is placed on the distal portion of the graft and the proximal clamp on the aorta is removed. This allows perfusion of the visceral and spinal vessels as the distal most anastomosis is performed. Alternatively, after the proximal anastomosis has been performed, the distal anastomosis is performed as one large spatulated anastomosis to include all the visceral vessels (Fig. 7.18). Not all thoracoabdominal aneurysms are anatomically suited to this simpler repair. Again, profound hypothermia and circulatory arrest have been advocated as alternatives to left atrial-femo-ral bypass again with excellent results.

Surgical judgment and modification of techniques tailored to meet individual needs is a necessity. For example, separate reimplantation of a button of spinal arteries may be necessary. In cases of "mega-aorta syndrome" (Fig. 7.19a-e), the entire aorta including ascending, transverse, descending thoracic, and thoracoabdominal aorta may be aneurysmal. The "elephant trunk" procedure, originally conceived by Hans Borst utilizes a staged sequence of aortic operations with each subsequent step simplified by the presence of a free-floating distal end of graft (Fig. 7.20a-b). On subsequent redo operations, achieving control of the distal graft is a simple matter (as opposed to taking down a distal graft to aorta anastomosis).

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