Aortic dissection

Question 1

Aortic dissection: Definition

Answer 1

• Aortic dissection describes the condition when a separation has occurred in aortic wall intima, causing blood flow into a new false channel composed of the inner and outer layers of the media.
• Dissection most commonly occurs with a discrete intimal tear, but can occur without one.
• An aortic dissection is considered acute if the process is less than 14 days old.

Question 2

Aortic dissection: Aetiology

Answer 2

• results from an intimal tear that extends into the media of the aortic wall
• Cystic medial degeneration predisposes to intimal disruption and is characterised by elastin, collagen, and smooth muscle breakdown in the lamina media
• Marfan syndrome and Ehlers-Danlos syndrome lead to weakening of the media
• non-specific connective-tissue diseases
• Aortic atherosclerosis with dilation, and inflammatory or traumatic conditions or infections, may also predispose to aneurysmal degeneration and dissection

Question 3

Aortic dissection: Risk factors

Answer 3

• hypertension
• atherosclerotic aneurysmal disease
• Marfan syndrome
• Ehlers-Danlos syndrome

Question 4

Aortic dissection: Pathophysiology

Answer 4

• An intimal tear is the initial event, with subsequent degeneration of the medial layer of the aortic wall.
• Blood then passes through the media, propagating distally or proximally and creating a false lumen.
• As the dissection propagates, flow through the false lumen can occlude flow through branches of the aorta, including the coronary, brachiocephalic, intercostal, visceral and renal, or iliac vessels.

Question 5

Aortic dissection: Cinical manifestations: key presentations, other symptoms and signs

Answer 5

• suspected when an abrupt onset of tearing or ripping chest or back pain is reported
• The usual presentation is a male patient in their 50s, but the condition may occur in younger patients who have
  
  • Marfan syndrome
  • Ehlers-Danlos syndrome
  • or other connective-tissue disorders.
• Most patients have prior hypertension, often poorly controlled
• Younger patients may have a connective-tissue disorder, or a recent history of heavy lifting or cocaine use
• The pain associated with aortic dissection may be located retrosternally, interscapularly, or in the lower back.
  
  • Anterior chest pain is typically associated with an ascending dissection;
  • interscapular pain usually occurs with a descending dissection.

Question 6

Aortic dissection: Investigations (diagnosis): 1st line, gold standard & other

Answer 6

Initial work-up includes chest x-ray, ECG, and cardiac enzymes to exclude pneumonia or MI

• ECG
  
  • to rule out MI
• CXR
  
  • may show widened mediastinum
  • can rule out other causes of pain
• cardiac enzymes
  
  • usually neg for AD
• negative D-dimer may be helpful to rule out aortic dissection but not specific enough when used in isolation to diagnose
• as soon as AD diagnosis suspected, order a CT angiography
• if renal perfusion is compromised
  
  • renal function tests
    
    • urea
    • creatine
• if hepatic function compromised
  
  • liver func tests
    
    • ALT
    • ALP
    • AST

Question 7

Aortic dissection: DDx

Answer 7

• Acute coronary syndrome
• Pericarditis
• Aortic aneurysm

Question 8

Aortic dissection: Management

Answer 8

Type A: ascending, type B: descending

• Supplemental oxygen and haemodynamic support with intravenous fluid resuscitation and judicious use of inotropes is recommended in cases of incipient renal failure and hypovolaemic shock.
• Initial management of both type A and B dissections involves intensive monitoring and anti-impulse therapy.
• IV beta blockade is used to achieve a heart rate less than 60 beats per minute and systolic blood pressure less than 120 mmHg.
• pain should also be controlled with intravenous opioids
  
  • it should be noted that morphine causes vasodilation and reduces the heart rate by increasing vagal tone.
• Essentially, damaged aorta needs to be surgically repaired/ replaced
• On discharge from hospital, BP control continued: beta-blockers and ACE inhibitors are usually required, with additional antihypertensives such as diuretics or calcium-channel blockers used if necessary.