Acute aortic syndrome: Spectrum of imaging appearances

The main objective of this paper is to illustrate and analyse the spectrum of MDCT findings of the entities that compose acute aortic syndrome (AAS) - namely acute aortic dissection (AD), intramural hematoma (IMH) and penetrating atherosclerotic ulcer (PAU) - discussing their pathophysiology. These related entities have a similar nonspecific clinical presentation mimicking other conditions such as myocardial infarction. Therefore, a high degree of clinical suspicion should prompt immediate confirmation by non-invasive imaging techniques which can modify its natural history, being MDCT the technique of choice, allowing accurate detection, characterization and complications evaluation in the Emergency Department.

A detailed analysis of a series of clinical case of acute aortic syndrome seen at our Department is done, counselling with a review of the state of the art regarding the pathologic mechanisms, diagnostic evaluation and therapeutic management.

They share a common feature of separation of the aortic walls. In AD there is an inward intimal displacement or tear, creating a true and a false lumen (double lumen). Detailing the extent, configuration - including true and false lumina distinction - and complications, are essential to proper treatment planning. IMH is defined by the presence of acute haemorrhage within wall layers without no visible intimal flap or tear on conventional techniques. It can lead to wall infarction and consequent dissection. PAU is due to erosion of internal elastic lamina - reaching the media - by an atherosclerotic plaque in the setting of advanced atherosclerosis or, less commonly, after rupture of a mycotic plaque or due to connective tissue disorders, appearing as an irregular focal contrasted outpouching outside the lumen. It can precipitate IMH or a pseudoaneurysm and progress, frequently, to dissection or rupture, coursing with high mortality, if not treated. Well known complications are aortic rupture with massive haemorrhage, pericardial tamponade by hemopericardium, mediastinal hematoma or hemothorax, pulmonary artery stenosis and/or pulmonary haemorrhage or organ ischemia.

MDCT findings knowledge allows a correct diagnosis. These life-threatening entities have an undistinguishable clinical presentation but different physiopathology mechanisms - reflected in differing radiologic findings - prognosis and management.