What are acute aortic syndromes?

Acute Aortic Syndromes: Definition and Classification

Acute aortic syndrome (AAS) encompasses three distinct but interrelated life-threatening conditions: acute aortic dissection (AD), intramural hematoma (IMH), and penetrating atherosclerotic ulcer (PAU). 1

The Three Entities of AAS

1. Acute Aortic Dissection (AD)

• Most common presentation of AAS, representing the majority of cases 1
• Defined as disruption of the media layer with bleeding within and along the aortic wall, resulting in separation of the aortic layers 1
• In 90% of patients, an intimal tear is present creating a double lumen separated by a septum 1
• Carries the highest mortality risk: untreated ascending AD has early mortality rates of 1-2% per hour after symptom onset 1
• Medical management alone of acute ascending AD results in 20% mortality by 24 hours, 30% by 48 hours, and 40-70% by day 7 1

2. Intramural Hematoma (IMH)

• Represents 10-25% of all AAS cases 1, 2
• Characterized by blood within the media layer without a visible intimal tear or flap 1
• Prevalence of isolated IMH in patients with suspected AAS is 21-30% 1
• Originates from ruptured vasa vasorum in the media layers 1
• Echocardiographically appears as ≥5 mm crescentic or circumferential heterogeneous thickening of the aortic wall 1
• Dynamic condition: 28-47% of patients progress to classic AD over time, while others resolve with or without aneurysmal enlargement 1

3. Penetrating Atherosclerotic Ulcer (PAU)

• An atherosclerotic lesion with ulceration that penetrates the internal elastic lamina, allowing hematoma formation within the media 2, 3
• Most commonly occurs in the mid and distal descending aorta 1
• More prevalent in elderly patients with advanced atherosclerosis 2
• Can be seen in isolation or in conjunction with AD and IMH 1
• May progress to classic dissection, particularly when involving the ascending aorta or aortic arch 1

Clinical Presentation

Cardinal Symptom

• Sudden onset of severe, tearing, or ripping chest pain is the hallmark presentation 1, 2
• Pain location varies: chest (80%), back (40%), abdomen (25%) 2
• Specifically described as anterior or interscapular back pain 1

Malperfusion Syndrome

• Symptoms may be dominated by malperfusion due to obstruction of the aortic lumen or side branches when intimal and medial layers are separated 1

Risk Factors

• Hypertension: present in 65-75% of cases, often poorly controlled 1, 2
• Family history of aortic disease 1
• Underlying collagen vascular disorders (e.g., Marfan syndrome) 1, 2
• Advanced age (mean presentation around 63 years) 1, 2
• Male predominance (65% of cases) 1, 2

Pathophysiology and Shared Features

All three conditions share a common pathophysiologic pathway: damage to the aortic wall with dynamic and overlapping mechanisms, similar clinical presentations, and common diagnostic and therapeutic approaches 2, 3. The major cause of early death with AAS is aortic rupture 1.

Imaging Findings

Imaging findings of AAS include any disruption of the intimal and medial layers, either with:

• IMH within the media (with or without a penetrating ulcer) 1
• An intimal flap (in classic dissection) 1
• Mushroom-shaped protrusion of the arterial lumen with outwardly facing edges (in PAU) 3