What does the syndrome include?
Acute aortic syndrome includes three pathologies:
- Aortic dissection (Aortic dissection): occurs when the intima tears. Blood enters the middle layer (media) and begins to dissect along the vessel wall. This is the most common cause of the syndrome (75%), most frequently involving the ascending aorta and aortic arch.
- Intramural hematoma (Intramural haematoma, IMH): bleeding within the vessel wall. It can originate from small nutrient vessels (vasa vasorum) or at the base of an ulcer. It occurs in 10–20% of cases, more commonly in elderly patients in the descending thoracic aorta.
- Penetrating aortic ulcer (Penetrating aortic ulcer, PAU): a deep ulceration of an atherosclerotic plaque penetrating directly into the media. It develops against the background of severe atheromatosis, usually in the descending aorta.
Classification and prognosis
Localization of the process is crucial for choosing management tactics. The Stanford classification is most commonly used:
- Type A (Stanford A): involves the ascending aorta. Without treatment, 20% of patients do not survive to reach the hospital. Thirty-day mortality with conservative management reaches 50%, while surgical intervention reduces it to 17%.
- Type B (Stanford B): affects the descending aorta distal to the left subclavian artery. In uncomplicated cases, 30-day mortality is around 10%. However, one-third of patients develop complications, which dramatically worsens the prognosis.
Based on the time of onset, the process is divided into acute (less than 14 days), subacute (from 14 days to 2 months), and chronic (more than 2 months). The main risk factor for developing these conditions is uncontrolled arterial hypertension.
Principles of treatment
Patients require emergency admission to the ICU with invasive monitoring. The cornerstone of conservative therapy is aggressive pain control, reduction of blood pressure, and heart rate control (using intravenous β-blockers and nitrates). This is necessary to reduce the stress on the ruptured aortic wall.
Further surgical management depends on the type of lesion:
- Type A: Endovascular methods are generally not suitable here. Patients require emergency open surgical intervention.
- Type B (uncomplicated): Careful monitoring and serial imaging are indicated. Additional endovascular repair (TEVAR) on top of optimal medical therapy improves 5-year survival.
- Type B (complicated): The presence of a rupture with blood extending outside the wall, malperfusion syndrome (organ ischemia), or rapid aortic expansion (greater than 4.5 cm) are absolute indications for urgent intervention.
Diagnostic imaging and complications
Cross-sectional imaging methods—CT or MRI—form the basis of diagnosis. On CT scans of an aortic dissection, the separated intimal flap (dissection flap) is clearly visible, dividing the vessel into true (true lumen) and false (false lumen) lumens.
The main problem of dissection is the occlusion of major aortic branches by the false lumen, causing malperfusion syndrome (ischemia).
The primary goal of endovascular treatment (TEVAR) is to cover the primary entry tear (entry tear) with a stent-graft. This causes a drop in pressure in the false lumen, making it collapse (and ideally thrombose), while the true lumen expands, restoring normal blood flow. If the false lumen continues to receive blood after stent placement (due to additional fenestrations further down the vessel), the risk of aneurysm formation persists.
Briefly: answers to topical questions
How to differentiate true and false lumens on CT images in aortic dissection?
On CT, the true and false lumens are separated by the intimal flap. The true lumen usually has a smaller diameter, may be compressed by the false lumen, and shows greater contrast enhancement. Volume rendering (VR) is used to visualize the intimal flap, the true and false lumens, as well as entry and exit sites.
What are the CT signs of intramural hematoma instability?
CT signs of severe instability in intramural hematoma may include indirect signs of impending rupture:
- Periaortic hematoma — a mass lesion surrounding the aortic contour.
- Hemorrhagic pleural effusion — its nature is confirmed by high attenuation on unenhanced CT (20–40 HU).
- Pericardial or mediastinal hematoma.
- Disease progression — the appearance of a right-sided pleural effusion or an increasing aortic diameter over time.
What anatomical landmarks are used to classify aortic dissection according to the DeBakey classification?
The following anatomical landmarks are used to classify aortic dissection according to the DeBakey classification: the ascending aorta, the aortic arch, the descending aorta (distal to the left subclavian artery), and the abdominal aorta.
| DeBakey Type | Dissection Localization |
|---|---|
| Type I | Ascending and descending aorta |
| Type II | Ascending aorta and arch only |
| Type IIIa | Descending thoracic aorta only |
| Type IIIb | Descending aorta extending into the abdomen |
What specific drugs are used for medical control of blood pressure and heart rate in acute aortic syndrome?
Intravenous $\beta$-blockers and peripheral vasodilators are used for medical control of blood pressure and heart rate in aortic dissection.
- Esmolol (Esmolol) is a $\beta$-blocker used in the initial phase of therapy.
- Labetalol (Labetalol) is an alternative drug for initial control.
- Nicardipine (Nicardipine) is administered as an infusion after $\beta$-blocker therapy.
An easy way to remember hemodynamic targets in the ICU is the "Double Sixty" rule: heart rate should be less than 60 beats per minute, and systolic blood pressure should be less than two times 60 (i.e., < 120 mmHg).
Class and exam questions
Can acute aortic syndrome be ruled out using an X-ray?
No. A normal chest X-ray does not rule out aortic dissection, intramural hematoma, or penetrating ulcer. CT or MRI is required for an accurate diagnosis.
What is the difference between dynamic and static branch occlusion?
Dynamic occlusion occurs when the intimal flap prolapses into the ostium of an aortic branch (compressing it). In static occlusion, the dissection line extends directly into the branch itself, causing local thrombosis.
How does a penetrating aortic ulcer appear on a CT scan?
It is visualized as an eccentric saccular outpouching of the aortic wall. A hyperdense area corresponding to an intramural hematoma is often identified nearby.
What else to study on this topic
- Prognostic factors for intervention in Type B dissection (expansion rate and false lumen diameter)
- Rupture anatomy and proximal defect closure technique using TEVAR
- Aneurysm formation as the main complication of chronic aortic dissection
- Blunt thoracic aortic injury: mechanism of shearing forces at the isthmus and management tactics
- Endovascular treatment of aortic coarctation: the issue of vessel elastic recoil
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