Results

There were 1,314 patients included in the study. The median age was 59 years with 49 percent being female. A total of 44 cases (3.3 percent) were diagnosed with AoD with 21 (1.5 percent) Stanford type A and 23 (1.8 percent) Stanford type B dissections. Additionally, 41 cases (93.2 percent) had at least one finding present on POCUS examination.

Key Results

While the sensitivity of POCUS for aortic dissection was high, the 95 percent confidence interval around the point estimate was very wide.

• Primary Outcome: Diagnostic accuracy of identifying Stanford type A and Stanford type B AoDs
• Secondary Outcomes: Test characteristics of each of the three individual sonographic findings for diagnosing Stanford type A and Stanford type B AoDs.

EBM Commentary

1. Convenience Sample: These were not consecutive patients but rather a convenience sample of patients with suspected AoD. This could have introduced selection bias into the study.
2. Ultrasonographers: POCUS was performed by PGY1–PGY3 emergency medicine residents. They received a four-hour introductory course taught by emergency ultrasound faculty. In addition, each resident completed a three-week emergency ultrasound rotation during their internship. They did not receive any additional formal training before participating in the study except for the standard bedside teaching throughout their residency. This may impact the external validity of the results to attending physicians in a non-academic, community, or rural settings.
3. Prevalence: The prevalence of 3.5 percent was high compared to previously published data.^5,6 This too suggests some selection bias. However, 3.5 percent is still a relatively small number and this results in a wide 95 percent confidence interval around the point estimate for the diagnostic accuracy metrics.

Bottom Line

Aortic dissections are rare diagnoses, deadly diagnoses and hard to diagnose even with POCUS.

Case Resolution

You perform the SPEED Protocol and do not see any of the three POCUS findings suggestive of AoD. This gives you some reassurance as it lowers the likelihood of this rare and deadly condition. However, the diagnostic accuracy of SPEED is not good enough to fully exclude the diagnosis and you order a CTA to definitively rule out an AoD in this man.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

Thank you to Dr. Neil Dasgupta who is an emergency medicine physician and ED intensivist from Long Island, NY for his assistance with this critical appraisal.