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    Acute Aortic Syndrome

    Cardiovascular

    Last Updated Nov 28, 2020
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    Context

    • This is a rare event, 3-5/100,000 cases per year but with a high mortality: 22% in type A; 1-2 % increase in mortality for every hour in delay to surgery.
    • Average age is 63: 75% between 40-70 yrs; 65% male; 65-75% history of hypertension.

    Two classification schemes:

    • Stanford:
      • Type A: Involves ascending aorta +/- descending aorta (60% of dissections).
      • Type B: Involves only the descending aorta.
    • DeBakey:
      • I – Ascending aorta which extends to at least the aortic arch +/- descending aorta.
      • II – Only the ascending aorta.
      • III – Only the descending aorta.

    Diagnostic Process

    • American Heart Association (AHA, 2010) developed an aortic dissection risk score, however it is retrospective, not validated, sensitivity 91% & specificity 40%.
    • AHA AD risk score sensitivity = 97% in very low risk patients, but specificity = 56%. Not useful in intermediate risk patients.
    • Canadian Clinical Practice Guidelines (2020) developed a clinical decision aid for assessing pre-test probability and recommendations for investigations. See table below:

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    • Once the pretest probability score is determined based on the clinical decision aid it can then be used to determine further diagnostic steps. Score=0: Low risk and no further testing required. Score=1: Moderate risk. Next step is to obtain d-dimer. Negative d-dimer then investigate other possible causes. Positive d-dimer, then ECG-gated CT aorta should be ordered. Score=2: High Risk and ECG-gated CT aorta should be ordered.

    Chest x-ray

    • Widened mediastinum (> 6cm upright PA film or > 8cm supine AP).
    • Up to 40-45% will be normal.

    Troponin

    • Positive in 25%.

    ECG

    • 1-2% may have ST elevation.

    D-dimer

    • AHA 2010 guideline do not use d-dimer for pretest probability analysis.
    • Canadian Clinical Practice Guidelines do incorporate d-dimer into pretest analysis.
    • ACEP 2014: DO NOT rely on d-dimer alone to exclude AD.

    Ultrasound

    • Transthoracic Ultrasound for aneurysmal dilatation of the aortic root Sensitivity: 60%, Specificity: 85% (Nazerian et al. 2019).
    • Having either a thoracic or abdominal aneurysm is associated with acute aortic syndrome. Point of care US (POCUS) is accurate in the diagnosis of Abdominal aortic aneurysm (Bentz et al. 2006) and should be performed as part of the pre test probability analysis. (Ohle et al. 2020).
    • ACEP 2014: CV surgical consult or immediate transfer to higher level of care if US positive for dissection.

    CT Scan

    • Gold standard.
    • Aortic dissection may be missed if only ordering CT PE studies. If clinical suspicion, need to order Aortic Dissection specific CT protocol.
    • Triple rule out CT angiography (Ayaram et al. 2013): insufficient data to rule out AD.

    Management

    • Decrease the BP and pulse if they are elevated.
    • European guidelines recommend SBP 100-120mmHg.
    • Use labetolol 20mg IV, onset is within 5-10 minutes, q10 min to max of 300mg.
    • May use a labetolol infusion at 2mg/min.
    • Insert an arterial line if possible.

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    Quality Of Evidence?

    Justification

    • AHA dissection score: Not a validated clinical decision score.
    • Canadian AAS Clinical decision Aid.
    • Treatment: No specific targets have shown reduction in mortality and morbidity.
    Low
    • Transthoracic Ultrasound: ACEP level B.
    Moderate

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