Background Information
Definition
Aortic dissection is a life-threatening condition:
- Due to a tear in the aortic intima → 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
- Pain may migrate as the dissection propagates
Possible examination findings: [Ref]
- Hypertension
- Note that hypotension / shock can occur in complicated dissection
- Aortic regurgitation features
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.
Always consider dissection before reperfusion: ~19% of dissections show ischaemic ECG changes and ~7% present as frank MI – usually inferior STEMI from RCA ostial involvement.
Features suggestive of dissection, including back pain, inter-arm BP differential, new AR murmur, widened mediastinum, or pericardial effusion/intimal flap on bedside echo should prompt immediate investigation for dissection (i.e., CT or echo), and withholding of thrombolysis and antithrombotic loading, without delaying transfer to a surgical centre.[Ref]
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 TOE
- TOE is preferred over TTE
- 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
- Presence of flap in the ascending aorta = type A dissection
- Flap confined to the descending aorta = type B dissection
- On TOE, 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 intervention is the top priority
Concurrent medical therapy (to reduce aortic stress) is indicated during initial stabilisation (but should not delay surgical input). |
| Stanford type B | 1st line: medical therapy
Complicated type B dissection may require intervention:
|
Medical Therapy
Medical therapy aims to reduce aortic stress and comprises:
- Adequate pain management is important (reduces sympathetic tone, thus HR/cardiac contractility)
- Opioids are typically 1st line
- Blood Pressure (Goal: <120 mmHg) / Heart Rate control (Goal: 60-80bpm)
- Step 1: IV beta blockers (esmolol or labetalol)
- Alternative to beta blockers: rate-limiting CCB (verapamil or diltiazem)
- Step 1: IV beta blockers (esmolol or labetalol)
-
- Step 2 (if target BP unmet) : add vasodilators (e.g. sodium nitroprusside)
- Vasodilators should only be added once the heart rate is well controlled with a beta blocker to prevent reflex tachycardia
- Step 2 (if target BP unmet) : add vasodilators (e.g. sodium nitroprusside)
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)
ACS caused by aortic dissection should be treated as a type A dissection and NOT on the ACS pathway.
- Any acute coronary syndrome presentation: ST elevation, NSTEMI or an isolated troponin rise — can be caused by aortic dissection extending into a coronary ostium. If dissection is suspected, do not treat on the ACS pathway: antiplatelets, anticoagulation and thrombolysis risk catastrophic haemorrhage and cannot relieve a mechanically obstructed ostium. Ensure blood pressure control, image the aorta, and refer for emergency surgical repair. [Ref]
Type B Aortic Dissection
Most type B dissections are treated medically, surgical intervention is NOT necessary for all patients
If surgical intervention is necessary → TEVAR is preferred
- TEVAR 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 TEVAR is not appropriate
References