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 (including those involving the aortic arch)

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 features

Other concurrent presentation / complications depending on the affected vessel: ^[Ref]

Artery involvement	Presentation
Subclavian artery	Pulse deficits Unequal arm pulses Unequal blood pressure (>20 mmHg difference)   Arm ischaemia / claudication
Coronary artery	Myocardial infarction
Carotid artery	Stroke Syncope
Mesenteric artery	Abdominal pain Mesenteric ischaemia
Renal artery	Acute kidney injury Haematuria
Spinal artery	Painless paraplegia
Iliac / femoral artery	Lower limb ischaemia

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

Diagnosis

Diagnostic Tests

Confirmatory test: CT angiography

• If unstable patients  → trans-oesophageal echo can be performed first

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 Normal ECG Nonspecific ischaemic changes (e.g., ST depression, T wave inversions) ST elevation
Chest X-ray	To exclude chest pathologies Possible chest X-ray findings in aortic dissection: Mediastinal widening Abnormal aortic contour Pleural effusion
D-dimer	Typically elevated Low D-dimer + low clinical risk score can be used to exclude aortic dissection NB that elevated D-dimer is non-specific and cannot confirm the diagnosis

Management

Management depends on the type of aortic dissection:

Aortic dissection type	Management
Stanford type A	Emergency surgical intervention 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 Blood control alone is sufficient for most patients Surgical intervention is NOT routinely indicated   Complicated type B dissection may require intervention: 1st line: TEVAR 2nd line: surgical intervention

Surgical Intervention

Type A Aortic Dissection

Type A aortic dissection always require 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 → 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

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 (esmolol  or labetalol)
  • 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