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The successful repair of an infected arterial anastomosis is often hampered by the need to leave prosthetic material at the site of infection. To determine whether an aortic defect could be repaired by direct closure with a muscle flap, thereby eliminating the need for prosthetic material, we subjected 33 young pigs weighing 17 to 19 kg to a left lateral thoracotomy under sterile conditions. An aortic defect 2 cm in diameter was created in the descending thoracic aorta just distal to the origin of the left subclavian artery. In one group (n = 11), this defect was patched with a freshly harvested but devascularized segment of chest wall muscle. In another group (n = 22), the aortic defect was patched with a vascularized chest wall muscle flap. Pigs were followed for up to 12 weeks and evaluated by arteriography and postmortem examination. There were no deaths or vascular complications attributable to the muscle flap repair in any pig. Pseudointimal formation began within 24 hours postoperatively and was of comparable thickness to the original arterial wall by 12 weeks. No aneurysmal changes were noted in any animal, and normal aortic luminal dimensions were preserved despite a tripling in mean body weight over the 12 week period. The loss of flap viability appeared to offer no threat to vascular integrity, as the free muscle patches, although undergoing cell necrosis and substantial remodeling, remained intact. These results demonstrate the short-term feasibility of using viable muscle flaps to patch aortic defects in situations wherein the use of prosthetic material would be undesirable.