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Aneurysm - Thoraco

Description of Clinical Program
An aneurysm is an abnormal enlargement of a portion of a blood vessel. On the arterial side of the circulation, this type of enlargement causes weakening of the wall of the artery with the potential for rupture or clot formation. The latter can dislodge and cause blockage in the circulation of the legs. Once an aneurysm reaches a certain size, the risk of rupture exceeds the risk of elective repair. Aneurysms commonly occur in the aorta, the main artery in the body. Most frequently, they are located below the kidney arteries. Current techniques for repair of abdominal aortic aneurysms include standard surgical repair and, more recently, endovascular repair where the arterial system is used as the access to the aneurysm, placing a stented graft to correct the abnormal enlargement. This avoids a major surgical intervention.

Aneurysms can occur in other portions of the aorta. When an aortic aneurysm involves the portion of the aorta in the chest and abdomen, these are termed thoracoabdominal aortic aneurysms. Although several types of thoracoabdominal aneurysms exist, they all share the same technical challenges in their management, Often they involve the area of the aorta where major branches to the liver, stomach, intestines and kidneys originate. Thoracoabdominal aneurysms also carry a risk of rupture or embolization. Because of this, repair is recommended once they reach a certain size.

Repair of thoracoabdominal aneurysms involves replacement of the aorta in those segments where major arterial branches supply vital organs. Thus, very specialized techniques are required in order to protect those organs during repair. At the UCLA Medical Center, repair of these aneurysms is undertaken using a team approach where specialists in anesthesia, thoracic and vascular surgery are involved in order to provide effective repair while minimizing risks. Our experience with thoracoabdominal aortic aneurysms has allowed us to proceed in an elective fashion in these very challenging cases while minimizing the risks of organ damage including spinal cord protection. The latter is perhaps the most feared complication which can render the patient with weakness or paralysis of both lower extremities. Techniques have been developed that reduce the risk of such complications to a minimum.

Based on our endovascular experience for the more common aneurysms in the aorta below the renal arteries, newer techniques are being applied to the management of thoracoabdominal aneurysms. These techniques involve the combination of standard surgical and endovascular technology. Repair of thoracoabdominal aneurysms remains a challenging problem. We anticipate that evolving technology and experience will continue to improve the results that can currently be accomplished.

Management of patients with thoracoabdominal aneurysm remains a challenging problem. When the aneurysm involves the visceral arteries, reimplantation of the renal and mesenteric vessels to assure adequate circulation to the abdominal viscera is necessary. In order to minimize the time of ischemia during surgical repair, we have utilized distal aortic perfusion with an extracorporeal pump which allows the circulation to be maintained to all visceral organs, including the kidneys, while the repair is ongoing. In a recent randomized trial this technique proved beneficial in minimizing organ dysfunction following surgical repair.

Spinal cord ischemia remains one of the most feared complications associated with thoracoabdominal aneurysm repair. Recent advances in the understanding of the pathophysiology of this complication have made significant contributions to the current approach in the management of these lesions. In particular, spinal catheter drainage allows the intraspinal pressure to be reduced so that perfusion pressure during aortic cross clamping is maximized. In combination with distal aortic perfusion and intercostal artery reimplantation, the incidence of paraplegia in our experience has been significantly reduced.

Unfortunately, many patients with thoracoabdominal aneurysm present to our institution acutely, usually with a contained rupture. In these instances, use of adjunctive measures to minimize risk are often not feasible because of the urgency of the intervention. It is therefore imperative that, just as has been done with infrarenal abdominal aortic aneurysms, patients with thoracoabdominal aneurysms be evaluated in a timely fashion in anticipation of elective reconstruction. This is perhaps as important as any other adjunctive measure in avoiding major complications.

Recent advances in endovascular grafting combined with our growing experience using endovascular repair for infrarenal abdominal aortic aneurysms, has allowed us to explore combined surgical and endovascular approaches to the management of complex thoracoabdominal aneurysms. This experience is evolving and is likely to expand in its applicability as the technology improves. Using combined surgical and endovascular techniques is likely to significantly improve the outcome of patients with these life-threatening aneurysms.

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