Background Information
Definition
Aortic dissection is a life-threatening condition:
- Due to a tear in the aortic intimaThis is the innermost layer of the aorta → blood flow between layers of the vessel wall
- This creates a false lumen, which can compromise blood flow and potentially rupture
Aetiology
Acquired causes: [Ref]
- Trauma (e.g. motor vehicle collision, during valve replacement surgery)
- Vasculitis (e.g. aortitis in tertiary syphilis, Takayasu arteritis)
Risk factors: [Ref]
- Hypertension – most important risk factor
- Male
- Older age
- Smoking
- Use of stimulant drugs (e.g. cocaine, amphetamines)
Congenital risk factors: [Ref]
- Connective tissue disorder – Marfan syndrome, Ehlers-Danlos syndrome
- Bicuspid aortic valve
- Coarctation of the aorta
Classification
The Stanford classification is more important, as it is used to guide management.
Stanford Classification
The Stanford classification depends on whether the ascending aorta is involved or not: [Ref]
| Type | Description |
|---|---|
| Stanford A | Any dissection that involves the ascending aorta (irrespective of the site of origin) |
| Stanford B | Any dissection that does NOT involve the ascending aorta (defined as distal to the left subclavian artery) |
DeBakey Classification
The DeBakey classification depends on the origin of the tear and the extent of the dissection:[ref]
| Type | Description |
|---|---|
| DeBakey 1 | Originates in the ascending aorta + extends beyond the arch |
| DeBakey 2 | Confined to the ascending aorta |
| Debakey 3 | Originates in the descending aorta (distal to the left subclavian artery) |
Clinical Features
Patients typically present with a sudden onset of: [Ref]
- Severe chest pain (most common) / upper back pain / abdominal pain
- Tearing / ripping in nature
- Maximal severity at onset
Possible examination findings: [Ref]
- Hypertension
- Note that hypotension / shock can occur in complicated dissection
- Aortic regurgitation featuresBounding pulse, widened pulse pressure, early diastolic murmur. This happens from root dilation
Other concurrent presentation / complications depending on the affected vessel: [Ref]
| Artery involvement | Presentation |
|---|---|
| Subclavian artery |
|
| Coronary artery |
|
| Carotid artery |
|
| Mesenteric artery |
|
| Renal artery |
|
| Spinal artery |
|
| Iliac / femoral artery |
|
Other concurrent presentation / complications depending on the compressed structure: [Ref]
| Structure involved | Presentation |
|---|---|
| Oesophagus | Dysphagia |
| Trachea / bronchus | Dyspnoea |
| Recurrent laryngeal nerve | Hoarseness |
| Sympathetic chain | Horner’s syndrome |
Classic presentation:
- Type A is more likely to present with anterior chest pain.
- Type B is more likely to present with back or abdominal pain (indicating abdominal aorta involvement).
Note that there is a significant overlap in practice, however this classic pattern is important for exams.
Diagnosis
Diagnostic Tests
Test of choice: CT angiography
- High sensitivity and specificity for dissection
- Allows comprehensive evaluation of the entire aorta and its branches, facilitates rapid triage and management decisions
For unstable patients (e.g. hypotension) → perform bedside TOETrans-oesophageal echocardiography
- TOETrans-oesophageal echocardiography is preferred over TTETrans-thoracic echocardiography
- Rationale: CT angiography may not be feasible due to hemodynamic compromise or inability to transfer the patient safely
- If type A aortic dissection is suspected based on trans-oesophageal echocardiogram, this is sufficient to proceed to surgical management
Imaging findings:
- On CT angiography, the hallmark finding is an intimal flap
The intimal flap is the thin sheet of torn intima that gets peeled away and ends up separating the true lumen from the false lumen.
In aortic dissection, a tear develops in the intima (the inner lining of the aortic wall). High-pressure blood then forces its way through this tear into the middle layer (media), creating a false lumen that runs alongside the normal true lumen.
- Presence of flap in the ascending aorta = type A dissection
- Flap confined to the descending aorta = type B dissection
- On TOE,Trans-oesophageal echocardiography the hallmark finding is a mobile dissection flap
Non-Diagnostic Tests
Recommended standard work-up in addition to definitive imaging (above):
| Test | Description |
|---|---|
| ECG | For rapid exclusion of acute coronary syndrome, which can present similarly to aortic dissection and may co-exist
Possible findings in dissection
|
| Chest X-ray | To exclude chest pathologies
Possible chest X-ray findings in aortic dissection:
|
| D-dimer | Typically elevated
|
Management
Management depends on the type of aortic dissection:
| Aortic dissection type | Management |
|---|---|
| Stanford type A | Emergency surgical interventionRecommended surgical approach involves: - Resection of primary intimal tear - Replacement of ascending aorta +/- root or arch repair - Restoration of flow to malperfused vessels is the top priority
Concurrent blood pressure control is indicated during initial stabilisation (but should not delay surgical input) |
| Stanford type B | 1st line: medical blood pressure control
CPlacement of a stent-graft via catheter through the femoral artery. TEVAR: thoracic endovascular aortic repairomplicated type B dissection- Uncontrolled hypertension despite medical therapy - Aortic rupture - Malperfusion syndrome (manifested as end-organ ischaemia, including renal, mesenteric, spinal or limb ischaemia) may require intervention:
|
Surgical Intervention
Type A Aortic Dissection
Type A aortic dissection always requires urgent surgical intervention (due to the risk of aortic rupture, aortic regurgitation, coronary obstruction, cardiac tamponade etc.)
Typical surgical approach for type A dissection:
- Open surgical repair via midline sternotomy
- Excision of the dissected segment → replacement with a Dacron (synthetic) graft
- +/- Aortic valve repair / replacement (if there is root / valve involvement)
Type B Aortic Dissection
Most type B dissections are treated medically, surgical intervention is NOT necessary for all patients
If surgical intervention is necessary → TEVARThoracic endovascular aortic repair is preferred
- TEVARThoracic endovascular aortic repair involves placing a stent graft via femoral access, the graft is placed in the descending thoracic aorta to seal off the false lumen created by the dissection
- Open surgical repair is 2nd line, only if TEVARThoracic endovascular aortic repair is not appropriate
Blood Pressure Control
Adequate pain management is important (reduce sympathetic tone, thus reduce heart rate)
- Opioids are typically 1st line
Target systolic BP target <120 mmHg:
- Step 1: IV beta blockers (esmololCardioselective beta-1 receptor antagonistor labetalolSelective alpha blocker and non-selective beta blocker)
- Alternative to beta blockers: rate-limiting CCB (verapamil or diltiazem)
- Step 2: add vasodilators (e.g. sodium nitroprusside, CCB)
- Vasodilators should only be added once the heart rate is well controlled with a beta blocker to prevent reflex tachycardia
References
RCEM Learning: Acute Aortic Dissection
2014 ESC Guidelines: diagnosis and treatment of aortic dissection
2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease