Guest post by Dr Daniel Bryant ACCS Trainee

There is no disease more conducive to clinical humility than aneurysm of the aorta.

William Osler

This a diagnosis you do not want to miss. Up to a 1/ 3 are though and this can lead to serious morbidity or even death. You need to stay vigilant and know when to include it in your differential diagnosis and investigate further. Luckily we have guidelines to help with this (below).

Definition of aortic dissection  “ A breach in the integrity of the aortic wall allowing blood to burst into the media of the aorta which is then spilt into two layers, creating a ‘false lumen’ alongside the true lumen.”

Risk Factors for Dissection of the Thoracic Aorta
  • Hypertension (80% of cases)
  • Connective tissue disease – Marfans,
  • Ehlers-Danlos syndrome
  • Known aortic aneurysm
  • Aortic coarctation
  • Bicuspid aortic valve
  • Previous aortic surgery
  • Trauma – either blunt chest trauma or iatrogenic
  • Pregnancy (usually 3 rd trimester)

Classification

Stanford System is more commonly used as more attuned to management strategy. Distinction between A and B is involvement/sparing of the ascending aorta. Type A dissections are the ones we can’t afford to miss in the ED with a mortality of 1-2% per hour for the first 24-48hrs, 75% at two weeks and 90% at a year.

aortic-dissection-classification


Presentation

Highly variable depending on site of dissection:

  • Chest/back pain
    • Sudden and central
    • Severe and typically ‘tearing’ or ‘ripping’
    • Often migratory – Chest then arm then abdomen
    • Anterior chest pain typically associated with ascending aorta dissections, back pain with descending aorta dissections  –
    • Potential for cardiac ischaemia (typically inferior MI) if coronary artery involvement
    • The pain experienced can be transient and patient appears pain free in the department.
    • A significant proportion of patients have no pain – then you have to use the symptoms below
  • Collapse/syncope
  • Neurological deficits (carotid artery involvement)
  • Paraplegia (spinal artery involvement)
  • Acute abdomen (mesenteric artery involvement)
  • Acute limb ischaemia – (usually leg due to common iliac involvement)
  • Renal failure (renal artery involvement)
  • Cardiac arrest

Clinical Signs

Again highly variable depending on site of dissection.

  • Hypertension (usually , though hypotension seen if frank rupture, AR or pericardial tamponade)
  • Unequal arm pulses
  • Systolic BP differential
  • Focal neurological deficit
  • AR murmur (if proximal extension of type A)
  • Signs of pericardial tamponade (if proximal extension of type A)
  • Shock
  • Absence of any or all of these signs will not exclude the diagnosis

Initial Investigations

  • ECG -Useful to look for alternative diagnosis (e.g. ACS) but ST elevation may be part of the dissection process.
  • Chest X-Ray
    • May be normal
    • Broadening of upper mediastinum
    • Irregular, widened aortic contour
    • Pleural effusion (L>R)
    • Depression of L main bronchus
    • Inward displacement of  aortic atherosclerotic calcification
AD1

Chest X-ray showing Aortic Dissection

 


Aortic Imaging

CT angiography is generally the investigation of choice – Specificity and sensitivity of  CTA approach 100%

TOE and MRI generally less readily available in ED. You might pick up a dissection flap on TTE but this isn’t sensitive enough to rule out dissection.

CTA showing aneurysmal dilation and a dissection of the ascending aorta (Type A)


Management

  • Time is critical – Early mortality for acute dissection is approx 1-2% per hour. 
  • Analgesia – IV opiates.
  • Blood pressure control if hypertensive – Typically labetalol to maintain a systolic BP below 120mmHg.
  • If you suspect Aortic Dissection you might want to start the above treatments while you are waiting for your emergency CTA.
  • Discussion withcardiothoracic centre in all cases:
    • Type A dissections require urgent surgical repair
    • Type B dissections generally managed medically
    • Our local centre is Bristol Royal Infirmary

Summary of Important Points

  • Clinical signs and symptoms can be highly variable.
  • Have a low threshold for dedicated aortic imaging if the diagnosis is suspected.
  • Prompt discussion with cardiothoracics once diagnosis established.
  • If you do not think of a diagnosis you will not make it.
  • Always have a low index of clinical suspicion in patients with chest/back pain particularly if known risk factors present.
  • New departmental guidelines on managing potential aortic dissections available now via ED guidelines website (intranet only, sorry) but you can check this article out for the gist and an excellent algorithm.

Other resources:

Tom Mitchell
Author: Tom Mitchell

Emergency Medicine Consultant UK