by Dr. Simon Moore MD CCFP
SNAP SAMP: List FIVE High Risk Features on physical exam for AAS (answer is below).
One out of every 2000 ER patients with chest or back pain have this life-threatening diagnosis.
ASSESSING FOR AAS IS AS EASY AS 1, 2, 3 . . .
In fact, 25% of patients with AAS have their diagnosis delayed by 24 hours. Don't miss it!
In a new Canadian guideline for AAS, your action depends on the patient's risk:
LOW RISK - No testing for AAS
MED RISK - D-dimer
HI RISK - ECG-gated CT aorta
EXAM TIP: Most questions can be answered in 10 words or less, but use as many words as you need to be descriptive. Write "ECG-gated CT aorta" and NOT just "CT" as an answer. This key guideline fits perfectly into the CFPC’s 105 topics as Chest Pain and now Shortness of Breath are priority topics.
How do you determine who is high risk? See the scoring tool below.
NEGATIVE D-DIMER RULES OUT AAS
A negative DD-dimer rules out AAS (<0.5% probability). A positive D-dimer necessitates an ECG-gated CT scan.
WHY NOT ORDER A D-DIMER FOR EVERYONE?
D-dimer for all comers will excessively increase the number of false positive CT scans.
HOW DO YOU DETERMINE WHO IS MEDIUM OR HIGH RISK?
The guideline authors use a risk calculator that is almost identical to the Aortic Dissection Detection Risk Score (ADD-RS) - see the easy-to-use calculator here, with some key changes marked with a * below:
Risk factors for patients
(Score one point for each except as noted)
*Connective tissue disease
Aortic valve disease
Recent aortic manipulation
Family history of AAS
*Aortic aneurysm = 2 points
HISTORY - Pain features
(Score one point if 1-2 risk factors, two points if more)
Severe or worst ever
Thunderclap or abrupt
Tearing or ripping
Migrating or radiating*
EXAM – High risk features
(Score two points if any are present)
Hypotension*
Pulse deficit
Neurologic deficit
New murmur of aortic regurgitation
Aortic aneurysm
LOW RISK = 0 points = No further investigations
MED RISK = 1 point = D dimer
HI RISK = ≥ 2 points = ECG - gated CT aorta
References:
CMAJ 2020 July 20;192:E832-43.
Circulation. 2018;137(3):250-258.
* = indicates a difference between the ADD-RS and the guideline