Aortic Dissection

Resident Clinical Pearl (RCP) – October 2017

Luke Taylor, R2 FMEM, Dalhousie University, Saint John, New Brunswick

Edited by Dr Kavish Chandra – @kavishpchandra

Reviewed by Dr. David Lewis

 

Why should we care?

• Aortic dissection remains difficult to diagnosis despite improvements in our understanding of the process and its characteristic features
• Many cases are still missed at the initial ED presentation
• Dissections occur after some violation of the intimal layer allows blood to enter the media and dissect between the intimal and adventitia. The blood flow entering the tear can extend the dissection proximally, distally, or both
• With each hour that passes there is a 1-2% increase in mortality as the dissection extends

 

History

The presentation is similar across all acute aortic syndromes (AAS)

• Acute intense chest or back pain (“SAH” of the torso)
• Ask about:
  • Location
  • Intensity at onset
  • Radiation of pain
• Aortic dissection can be painless ~5% of the time

IRAD 12 features most associated with acute aortic dissection

• The characteristic tearing/ripping was not found to be a common descriptor in International Registry of Aortic Dissection (IRAD)

Pearl : When assessing a patient with chest pain (CP), think CP+ 1 (see EMCases episode 92)

• CP+ CVA
• CP+ paralysis
• CP+ hoarseness
• CP+ limb ischemia

These features should drastically increase your suspicion for dissection

 

Physical examination

• Keep in mind a large portion of general population have a BP differential >10mmHg
• Vital signs can be normal but patients may have variation in their pulse or BP in the form a pulse deficit, SBP differential, hypertension or hypotension
  • Pulse Deficit: feel for difference between heart rate and the pulse rate
• Murmur of aortic insufficiency:
  https://www.youtube.com/watch?v=aGLTJduxwvw
• Neurological findings: objective focal neurological deficit

 

Investigations

• CXR: Look for a wide mediastinum, loss of aortic knob, calcium sign
  • A normal CXR does not rule out aortic dissection as 1/3 of CXRs in aortic dissection are normal
  • Pearl : Measure the distance from the white line to the outer edge of the aortic knob. A distance >0.5cm is considered a 

positive calcium sign

https://radiopaedia.org/articles/tangential-calcium-sign

 

• POCUS: If attempting, look for a dissection flap in the parasternal long axis view above the aortic valve. The flap may also be visible in abdominal aorta
  • Low sensitivity, but high specificity

• Look for pericardial effusion from a retrograde dissection into the pericardium

http://rubble.heppell.net/chestnet/t/ecgtut.htm

• Check out this FOAMed link in a patient presenting with ST elevations on their ECG
  http://edeblog.com/2014/02/pocus-for-aortic-dissection-a-case-2/

• But don’t let POCUS delay definitive imaging when searching for an intimal flap

 

• Laboratory:
  • Troponin: 1/4 of all dissections will have positive troponin so do not change your diagnosis based on a positive troponin
  • D-dimer: maybe some day but not ready for prime time
    http://rebelem.com/the-advised-trial-a-novel-clinical-algorithm-for-the-diagnosis-of-acute-

 

 

FOAMED Links and Resources

http://edeblog.com/2014/02/pocus-for-aortic-dissection-a-case-2/

https://emergencymedicinecases.com/aortic-dissection-em-cases-course/

http://circ.ahajournals.org/content/112/24/3802

https://lifeinthefastlane.com/collections/ebm-lecture-notes/aortic-dissection/

https://first10em.com/2017/02/07/d-dimer-aortic-dissection/

 

This post was copyedited by Kavish Chandra @kavishpchandra