Aortic Dissection

Aetiology/Causes:

• Most cases are linked to conditions that weaken the aortic wall, i.e., hypertension, connective tissue disorders (e.g., Marfan syndrome, Ehlers-Danlos syndrome), or pre-existing aortic aneurysms.

Risk Factors:

• Age: >60 years. 

• More common in males (2:1 ratio).

• Hypertension (most common risk factor)

• Genetic disorders: Marfan syndrome, Ehlers-Danlos syndrome

• Pre-existing aortic aneurysm

• Bicuspid aortic valve

• Coarctation of the aorta

• Turner syndrome

• Aortic instrumentation/surgery history

• Inflammatory conditions: giant cell arteritis, Takayasu arteritis, rheumatoid arthritis

• Pregnancy (especially third trimester and postpartum)

• Fluoroquinolone use

• Trauma: e.g., motor vehicle accidents.

• High-Intensity Physical Activities or Drug Use: e.g., cocaine

Pathophysiology:

• Dissection begins with a tear in the intimal layer, allowing blood to enter the media and create a false lumen.

• The dissection can propagate proximally or distally, potentially involving branch vessels.

• Complications can include rupture into surrounding structures (pericardium, pleural space, or abdomen) and occlusion of aortic branch vessels.

Symptoms:

• Pain: Sudden onset, severe, tearing, or ripping in nature, typically in the anterior chest (ascending dissection) or back (descending dissection). May radiate to the neck, jaw, or limbs.

• Neurological Symptoms: Syncope, hemiparesis, or stroke due to involvement of the carotid or subclavian arteries.

• Symptoms of Aortic Insufficiency: Dyspnoea, orthopnoea, or acute heart failure.

• Hypotension or Shock: Indicates rupture or tamponade.

• Other Symptoms: Flank pain, abdominal pain, or limb ischaemia.

Differential Diagnosis:

• Acute myocardial infarction (especially STEMI)

• Pulmonary embolism

• Pericarditis

• Pneumothorax

• Musculoskeletal pain

• Gastrointestinal perforation

• Ruptured aortic aneurysm

Investigations:

Initial Tests:

• CXR: May show a widened mediastinum or pleural effusion.

• ECG: To exclude myocardial infarction.

• Cardiac Enzymes: If myocardial ischaemia is suspected.

• UEC and Lactate: Assess renal function and tissue perfusion.

Definitive Imaging:

• CT Aorta (with contrast): Diagnostic test of choice; visualizes the intimal flap.

• Transoesophageal Echocardiography (TOE): Useful if CT is contraindicated or for unstable patients.

• MRI Aorta: Alternative imaging if radiation exposure is a concern.

Management:

Emergency measures:

• Stabilise haemodynamics: Aim for systolic BP 100-120 mmHg

• Intravenous beta-blockers (e.g., labetalol, esmolol): To reduce heart rate and shear stress on the aortic wall

• Analgesia: Morphine for pain control

Surgical vs. Medical Management:

• Type A dissection (ascending aorta involvement): Immediate surgical intervention

• Type B dissection (descending aorta): Medical management initially if uncomplicated; surgical or endovascular repair for complications (e.g., persistent pain, rupture, ischaemia)

Initial Stabilisation:

• Blood Pressure Control: IV beta-blockers (e.g., labetalol) to reduce shear stress; aim for systolic BP 100–120 mmHg.

• Analgesia: Morphine for pain control.

Definitive Management:

• Type A (proximal): Requires urgent surgical repair due to risk of aortic rupture and cardiac tamponade.

• Type B (distal): Treated medically unless complications (e.g., rupture, end-organ ischaemia) arise; endovascular stent grafting may be considered.

Long-Term Monitoring:

• Regular imaging (CT/MRI) for monitoring.

• Antihypertensives: Long-term BP control.

Complications:

• Aortic rupture: Life-threatening and often fatal

• Cardiac tamponade

• Organ ischaemia: Stroke, mesenteric ischaemia, renal failure

• Aortic regurgitation: Secondary to aortic valve involvement.

• End-Organ Ischaemia: E.g., stroke, acute kidney injury.

• Chronic Dissection: May lead to aneurysm formation.

Prognosis:

• Mortality is high without prompt treatment; survival improves significantly with early diagnosis and intervention. Type A dissections carry a higher mortality risk if not treated surgically.

Notes:

Classification:

• DeBakey Classification:

  • Type I: Involves both the ascending and descending aorta

  • Type II: Confined to the ascending aorta

  • Type III: Confined to the descending aorta

• Stanford Classification:

  • Type A: Involves the ascending aorta (with or without descending involvement)

  • Type B: Involves only the descending aorta