Chapter30 Aorta

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Chapter 30: Thoracic Aorta

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Figure 30.40.  Penetrating Atherosclerotic Ulcer (PAU) With Intra- mural Hematoma (IMH). Axial CT image at the level of the aortic arch demonstrates the focal outpouching of contrast ( arrow ) extend- ing beyond the surrounding intimal calcifications ( arrowheads ) con- sistent with a PAU. The PAU has eroded into the aortic media with surrounding intramural hematoma ( * ).

Figure 30.41.  Proximal Descending Aorta Pseudoaneurysm. Sagit- tal CT image in a 68-year-old woman demonstrates a large saccular pseudoaneurysm ( P ) along the inferior aspect of the aortic arch and descending thoracic aorta. A relatively narrow neck ( yellow arrows ) connects the aorta to the pseudoaneurysm. This represents a con- tained aortic rupture.

ligamentum arteriosum. Postoperative pseudoaneurysms are typically seen along the ascending aorta at the sites of aortic puncture, cannulation, and/or cross-clamping. Thoracic aortic pseudoaneurysms may be complicated by aortoenteric and/or aortobronchial fistulas, mediastinal hemorrhage, hemotho- rax, and pulmonary hemorrhage. Chest radiographs are of limited sensitivity and specific- ity for diagnosing pseudoaneurysms. Findings are similar to those in thoracic aortic aneurysm and may include widen- ing of the mediastinal/aortic contour. Pseudoaneurysms of the aortic arch or proximal descending aorta may lead to tracheal deviation and/or left upper lobe atelectasis. Tho- racic CTA is the primary imaging modality, with essentially 100% sensitivity and specificity for detecting pseudoaneu- rysms. The characteristic focal irregular outpouching/extrav- asation of contrast beyond the aortic lumen with a narrow neck (Figs.  30.41 and 30.42) is usually easily distinguish- able from the concentric enlargement of a true aneurysm. CT is also particularly useful in assessing extent of medias- tinal hematoma and associated complications. As discussed below, traumatic pseudoaneurysms are most common at the aortic isthmus. As pseudoaneurysms represent contained aortic rupture, they must be treated emergently via either open surgical repair or endovascular covered stent placement. Untreated pseudo- aneurysms progress (Fig. 30.43) eventually to aortic exsangui- nation and death. Aortic Fistulas Aortic rupture can occur in a multitude of settings including trauma, aortopathy, degenerative atherosclerosis, inflamma- tion, and infection. The aorta can rupture and hemorrhage freely into the mediastinum or, rarely, communicate with a

distinct anatomic space via a fistula. Aortic fistulas can form with the adjacent esophagus (i.e., aortoesophageal fistula) (Fig. 30.44), pleura (i.e., aortopleural fistula) (Fig. 30.45), bronchi (i.e., aortobronchial fistula) (Fig. 30.42), or other car- diovascular structures. Aortoesophageal fistulas can occur with aneurysm rup- ture, PAU, foreign body ingestion with esophageal per- foration, intrathoracic malignancies such as esophageal cancer, and postaortic endovascular stenting. Aortobron- chial fistulas have been reported in cases of prior bronchial intervention such as stenting and thoracic surgery such as lobectomy. Patients with aortoesophageal and aortobron- chial fistulas present most commonly with hematemesis and/ or hemoptysis. On imaging, extravasation of aortic contrast into an adjacent structure is pathognomonic but is not always seen. Secondary signs of aortic fistulas include a periaortic gas-containing collection mimicking an abscess, pseudoan- eurysm, and effacement of the normal periaortic fat plane. Aortic fistulas are typically lethal if not surgically treated, although endovascular aortic repair may serve as a bridge to open repair in the emergent setting.

Acute Traumatic Aortic Injury

Acute traumatic aortic injury (ATAI) represents a spectrum of disease from mild, focal injuries to the endothelium (“minimal intimal injury”) to contusion/IMH to mural disruption with pseudoaneurysm or rupture. ATAI most often occurs sec- ondary to high-energy blunt trauma—the classic scenario