Acute ascending thoracic aortic rupture due to penetrating atherosclerotic ulcer

Clinical History

A 68-year-old female went to the emergency department because of dizziness, with no dyspnoea or thoracic pain. She was hypotensive, with diminished peripheral pulses. After beginning fluid replacement, she became cyanotic and developed severe sinusal bradycardia first and asystole minutes later. The patient recovered quickly after continuous chest compression.

Imaging Findings

A chest radiograph and computed tomography (CT) were requested in order to exclude acute pulmonary thromboembolism and acute aortic disease. The chest radiograph showed widened mediastinum and cardiac silhouette (figure 1). Contrast-enhanced CT scan showed no filling defects in the pulmonary arteries and main branches, excluding acute pulmonary thromboembolism. However, pericardial effusion with near 70 Hounsfield Units (HU) was found, as well as stranding of the mediastinal fat, predominantly at the level of aortic-pulmonary window and Barety space (figure 2, 3). Evaluation of the thoracic aorta revealed a 9 mm outpouching of the ascending thoracic aorta, suggesting an atherosclerotic penetrating ulcer and an intramural hematoma (figure 4, 5). Due to the presence of haemorrhagic pericardial effusion and probable hemomediastinum, acute aortic rupture was presumed. The diagnosis was surgically proven.

Discussion

A penetrating atherosclerotic ulcer (PAU) is an ulcerating atherosclerotic lesion that penetrates the elastic lamina and is associated with hematoma formation. It is more commonly found in the middle or distal third of the thoracic aorta. In the ascending aorta, PAU is uncommon because rapid flow from the left ventricle provides protection against atherosclerosis(1-4).

While confined to the intimal layer, an atherosclerotic ulcer tends to be asymptomatic. These ulcers may progress to deep lesions that penetrate the elastic lamina and extend to the media, usually associated to hematoma formation. Hematoma typically develops within the media of the aortic wall and may present as a “double-barreled” or a “thrombosed” aortic dissection, the first demonstrating a communication between the true and false lumen, and the second one (more prevalent) showing no opacification of the false lumen. A saccular aneurysm is often found as a consequence of stretching of the weakened aortic wall. Both dissection and aneurysm may rupture (1-3,5-7).

PAU is typically a condition of elderly hypertensive men and remains silent until rupture occurs. Clinical rupture presentation is unspecific, usually with acute chest, retrosternal or interscapular pain. No clinical distinction is possible between PAU, aortic dissection, and aortic rupture (2-6,8). These entities may therefore be distinguished through imaging analysis, essentially using computed tomography (CT) and magnetic resonance imaging (MRI) (1,9). Angiography is no longer considered a first-line choice for diagnosis purposes. Transesophageal echocardiography may be also used but is operator dependent and is not accessible in all centers (1,10).

CT with angiographic study is usually the first choice, due to short acquisition times and possibility of multiplanar reconstruction. CT identifies a focal outpouching of the arterial internal contour, typically with adjacent parietal hematoma. Intimal calcifications may be found interiorly to the hematoma. Aortic wall thickening and enhancement may be also found (1-3,5). MRI has some advantages when compared to CT: lack of ionizing radiation and possibility of getting multiplanar imaging without using contrast material. Moreover, MRI is apparently superior to CT in differentiating acute intramural hematoma from non-acute conditions like stable atherosclerotic plaques and chronic intraluminal thrombus (1).However, CT has important advantages in the emergency setting. It is a more accessible and faster technique, also allowing differential diagnosis with other acute thoracic conditions.

The most widespread treatment for PAU is medical therapy. Surgery is performed in patients who have hemodynamic instability, persistent pain, aortic rupture, distal embolization, or rapid enlargement of the aortic diameter (4,11).

Differential Diagnosis List

Final Diagnosis

Ascending Thoracic Aorta Penetrating Ulcer

URL:	https://www.eurorad.org/case/12305
DOI:	10.1594/EURORAD/CASE.12305
ISSN:	1563-4086