A 59-year-old man presents to your community emergency department (ED) with chest pain that is radiating to his back. His vital signs are normal and the ECG does not demonstrate a myocardial infarction. Your clinical gestalt has you suspecting an acute aortic dissection (AoD). While waiting for laboratory investigations, including troponin and d-dimer, you wonder if a quick point-of-care ultrasound (POCUS) examination looking for three sonographic findings could help determine the likelihood of this being an AoD.

Background

Aortic syndrome (AAS) has been called the lethal triad and includes AoD, intramural hematoma (IMH), and penetrating aortic ulcer.¹ It is a deadly but rare condition that can present in atypical ways leading to delays in diagnosis associated with increased mortality.

AoD is broadly classified into two major types according to the Stanford classification system: Type A and Type B. This system is based on the location of the tear and helps guide treatment strategies. Type A dissections involve the ascending aorta and may extend into the descending aorta. It is more common and more dangerous than Type B, as it can lead to serious complications like rupture into the pericardial space leading to cardiac tamponade, aortic valve insufficiency, or myocardial infarction. Type B dissections occur in the descending aorta only, after it has passed the arteries that supply blood to the arms and head. They are less common than Type A and usually less immediately life-threatening, but still serious and potentially fatal if not treated properly.

Speed is important in making the diagnosis of an AoD due to the associated increase in mortality with delays.^2,3 There are clinical decision tools available, but the American College of Emergency Physicians does not recommend the routine use of these tools in suspected cases of AoD.⁴

Clinical Question

In patients with a suspected AoD, what is the diagnostic accuracy of three sonographic findings?

Reference

Gibbons RC, Smith D, Feig R, et al. The sonographic protocol for the emergent evaluation of aortic dissections (SPEED protocol): A multicenter, prospective, observational study. Acad Emerg Med. 2024;31(2):112-118.

• Population: A convenience sample of adult patients with clinically suspected Stanford type A or B AoDs before performing a POCUS or CTA from January 2010 to December 2019
  • Excluding: Patients unable to consent, those with a pre-existing or traumatic AoD, and individuals who did not receive a POCUS evaluation before advanced imaging (CTA, MRA, or TEE).
• Intervention: POCUS performed by PGY1 to three emergency medicine residents to identify three sonographic findings consistent with acute aortic dissection. This included (1) the presence of either a pericardial effusion or (2) an intimal flap, or (3) an aortic outflow track diameter greater than 35 mm measured from the inner wall to the inner wall within 20 mm of the aortic annulus during end-diastole.
• Comparison: CTA of chest-abdomen-pelvis, MRI/MRA, or cardiology-performed TEE
• Outcome:
  • Primary Outcome: Diagnostic accuracy of identifying a Stanford Type A and B AoDs
  • Secondary Outcomes: Test characteristics of each of the three individual sonographic findings for diagnosing Stanford type A and B AoDs
• Type of Study: Multicenter, prospective, observational, cohort study of a convenience sample of adult patients.

Authors’ Conclusions

The SPEED protocol has an overall sensitivity of 93.2 percent for AoD.

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