Chapter30 Aorta

788

Section V: Cardiac Radiology

A

B

Figure 30.51.  Graft Infection With Perigraft Abscess. Axial images through the lower abdomen in a patient 3 months status postendovascular stent repair of an abdominal aneurysm. Small focus of gas ( white arrow , A ) near the left common iliac artery is abnormal this late post repair. Contour irregularity of the left posterolateral abdominal aorta, which is contiguous with a left psoas abscess ( black arrow , B ).

of aortic pathology and whether the patient is a poor surgi- cal candidate. Since stents are rigid compared to grafts, stent grafts are more easily placed within the straight descending thoracic aorta, as opposed to the curved ascending aorta and aortic arch. Stent–grafts are designed to expand within the aortic lumen and closely appose with the aortic wall, thereby occluding intimal tears or covering atherosclerotic ulcers or pseudoaneurysms. Stent grafts are usually covered with a synthetic membrane which is not visible on imaging. In some instances, the proximal end of a stent graft is placed in the aortic arch and occludes the left subclavian artery. In this instance, the subclavian artery will fill via retrograde flow from the left vertebral artery. Before this is done, the surgeons need to ensure that the basilar system is complete, allowing for collateralization and that the left vertebral artery does not arise directly from the aortic arch. Endoleak complications of stent grafts in the thoracic aorta are the same as those in the abdominal aorta and occur in 29% of patients post TEVAR of TAAs. Endoleak is characterized by contrast external to the stent graft and represents continued blood flow within the excluded aortic lumen, which can result

increasing perigraft air can be caused by fistulization to an adjacent bronchus or esophagus (Fig. 30.44). Other signs of fistula include tethering to and contrast leak into the adjacent structure (Fig. 30.52). Postoperative pseudoaneurysm is a contained rupture that manifests as a contrast-containing collection contiguous with the aortic lumen, usually occurring at the anastomotic margins (Fig. 30.52). Graft reinforcements such as felt and pledgets are hyperattenuating and can be mistaken for contrast leak, mimicking a pseudoaneurysm. In these instances, noncontrast comparison imaging is essential to distinguish contrast from surgical material. Thoracic Endovascular Aortic Repair Thoracic endovascular aortic repair (TEVAR) entails place- ment of a metallic stent–graft into the aorta via an endovascu- lar approach. Indications for TEVAR include aortic dissection, PAU, pseudoaneurysm, and enlarging aneurysm. TEVAR may be preferred to open surgical repair depending on location

PA

PA

A

B

C

Figure 30.52.  Graft Pseudoaneurysm and Fistula. Noncontrast coronal ( A ), arterial phase coronal ( B ), and arterial phase axial ( C ) images. On noncontrast CT ( A ), there is calcification of the synthetic graft material ( white arrow ). Postcontrast ( B, C ), there is a contrast-filled collection ( black arrows ) located between the graft (white arrows) and the pulmonary artery ( PA ). A defect is present at the distal anastomotic site of the graft ( yellow arrow, B ), with a large pseudoaneurysm extending inferiorly ( black arrow , B ). Axial image (C) shows that the pseudoaneurysm ( black arrow , C ) partially wraps around the repaired ascending aorta ( white arrow , C ). Interestingly, the pseudoaneurysm has fistulized with the right pulmonary artery ( yellow arrow , C ).