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Aortic Dissection

by | 4 Nov, 2020

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Introduction

Aortic dissection refers to bleeding within and along the wall of the aorta and separation of the layers of the vessel. It usually begins with a tear in the tunica intima.

A false lumen develops alongside a true lumen. The aortic valve may be damaged and the branches of the aorta compromised. Typically, the false lumen re-enters the true lumen, creating a double-barrelled aorta. The false lumen may thrombose over time.

Classification

Stanford classification (modern)

Type A (66%): involves ascending aorta, with or without descending aorta

Type B (34%): involves only the descending aorta, beginning after the subclavian artery

DeBakey classification (old, deprecated)

I: ascending and descending aorta involved

II: only in ascending aorta

III: only descending aorta

Epidemiology

Affects 3-100,000. Males affected more than females (2:1 male:female). Peak incidence is in ages 50-70.

Causes

Dissections can occur as a result of:

  • Tear in intima and subsequent propagation of blood into media (90%)
  • Intramural haemorrhage and haematoma formation in media followed by intimal perforation

An intimal flap is characteristic of dissections.

Risk factors

  • Hypertension
  • Connective tissue disorders e.g. Marfan’s syndrome, Ehlers-Danlos syndrome, Turner’s syndrome
  • Congenital cardiovascular abnormalities e.g. bicsuspid aortic valve, coarctation of aorta
  • Pregnancy
  • Cocaine use
  • Iatrogenic – surgery to aorta e.g. aortic valve replacement, CABG
  • Decelaration trauma
  • Vasculitis

Clinical features

Sudden onset severe central chest pain. The pain has a tearing/stabbing character and may radiate to the back, arms and neck.

Other features include:

  • Sweating and pallor
  • Hypotension
  • Blood pressure discrepancy between upper limbs
  • Aortic regurgitation
  • Syncope

Investigations

  • Chest x-ray
  • ECG: exclude STEMI
  • CT and echocardiography: confirm diagnosis
  • MRI: can be used in stable patients

Management

Resuscitate with:

  • High-flow oxygen
  • Fluids
  • Analgesia
  • Beta-blockers

Stanford type A

Urgent surgical treatment to replace the ascending aorta with a graft. Control blood pressure whilst awaiting surgery e.g. beta-blockers (calcium channel blockers if beta-blockers contraindicated)

Stanford type B

Medical management with beta-blockers (calcium channel blockers if beta-blockers contraindicated).

Complications

  • Cardiac:
    • Aortic regurgitation
    • Myocardial infarction
    • Tamponade
  • Syncope
  • Neurological e.g. stroke, spinal cord ischaemia
  • Pulmonary e.g. pleural effusion
  • Gastrointestinal e.g. mesenteric ischaemia
  • Limb ischaemia

Prognosis

Mortality rate in type A is 25%, whilst type B is 10%.

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