Table 3:

Comparison of Canadian guideline recommendations to American Heart Association and European Society of Cardiology guidelines^*

Characteristics	Canadian guideline	American Heart Association20	European Society of Cardiology21
Clinical features
Aortic aneurysm	Definition History of thoracic or abdominal aortic aneurysm Bedside ultrasound with aortic dilation Widened mediastinum on chest radiograph Recommendation If present in isolation, high probability	Definition History of thoracic aneurysm Recommendation If present in isolation, intermediate probability	Definition History of thoracic aneurysm Recommendation If present in isolation, low probability
High-risk pain features	Definition Chest, back or abdominal pain described as: Abrupt or thunderclap Severe or worst ever Tearing or ripping Migrating or radiating Recommendation None present, low probability 1 or 2, intermediate probability 3 or more, high probability	Definition Chest, back or abdominal pain described as: Abrupt onset or severe; and Tearing or ripping, or sharp or stabbing Recommendation None present, low probability If pain described as above, intermediate probability	Definition Chest, back or abdominal pain described as any of the following: Abrupt Severe Tearing or ripping Recommendation None present, low probability 1 or more present in isolation, low probability
Blood pressure differential > 20 mm Hg	Recommendation Not part of pretest probability assessment	Recommendation If present in isolation, intermediate probability	Recommendation If present in isolation, low probability
Aortic regurgitation	Definition New murmur or aortic regurgitation with pain Recommendation If present in isolation, high probability (ECG-gated CT aorta)	Definition New murmur or aortic regurgitation with pain Recommendation If present in isolation, intermediate probability	Definition New murmur or aortic regurgitation with pain Recommendation If present in isolation, low probability
Pulse deficit	Recommendation If present in isolation, high probability	Recommendation If present in isolation, intermediate	Recommendation If present in isolation, low probability
Neurological deficit	Recommendation If present in isolation, high probability	Recommendation If present in isolation, intermediate probability	Recommendation If present in isolation, low probability
Hypotension	Definition Systolic blood pressure < 90 mm Hg or a shock index > 1	Definition Systolic blood pressure < 90 mm Hg	Definition Systolic blood pressure < 90 mm Hg
Hypotension	Recommendation If present in isolation, high probability	Recommendation If present in isolation, intermediate probability	Recommendation If present in isolation, low probability
Pericardial effusion	Recommendation If present in isolation, high probability	Not included in pretest probability assessment	Recommendation If present in isolation, high probability
Pretest probability
Low	No further testing	Consider CT aorta if no alternative diagnosis	Perform D-dimer, chest radiograph, transthoracic echocardiography
Intermediate	D-dimer	Expedited CT aorta if no alternative diagnosis	No intermediate probability category
High	ECG-gated CT aorta	ECG-gated CT aorta	ECG-gated CT aorta

Note: ECG = electrocardiogram, CT = computed tomography.
↵* “If present in isolation” refers to the presence of the sign or symptom in isolation. If the sign or symptom is present in context of other high-risk features for AAS, this changes the probability. See the full guideline (Appendix 1) for further information. Definitions for signs and symptoms associated with AAS are described in Appendix 2.