Emergency physician focused cardiac ultrasound improves diagnosis of ascending aortic dissection

Thomas Dunne - M4

Article: Pare, J. R., Liu, R., Moore, C. L., Sherban, T., Kelleher Jr, M. S., Thomas, S., & Taylor, R. A. (2016). Emergency physician focused cardiac ultrasound improves diagnosis of ascending aortic dissection. The American journal of emergency medicine, 34(3), 486-492.

Idea: Ascending aortic dissection (AAD) is an uncommon, however time-sensitive and potentially fatal disease process that proves difficult to diagnose in the emergency setting due to nonspecific symptoms and presentation. Although often definitively diagnosed through contrast enhanced computed tomography angiography (CTA), ordering CTA imaging on all patients with chest or back pain is infeasible. AAD has been shown to have an association with proximal aortic dilatation (90% of patients having dilatation greater than 4 cm at the time of diagnosis) that can be identified on Emergency Physician focused cardiac ultrasound (EP FOCUS). Additionally, aortic dilatation identified by FOCUS has been shown to be 70% sensitive for diagnosing AAD. The purpose of this study was to determine whether patients who received EP FOCUS and proximal thoracic aorta evaluation were diagnosed with AAD at least 1 hour earlier than patients who did not receive EP FOCUS and were eventually diagnosed as having AAD.

Study: This study was a retrospective cohort analysis of patients treated within a multihospital healthcare system who were found to have AAD during a 26-month study period from March 1, 2013 to May 1, 2015.

Design: Involved 3 affiliated sites with a single academic emergency ultrasound section responsible for POCUS education and quality assurance. All diagnostic information was obtained from study patient’s EHR and FOCUS interpretations and measurements were obtained from Qpath. Medical record abstraction was done both electronically and manually. All manual abstractors were trained prior to reviews. Authors performing medical record abstraction were blinded to time to diagnosis. An independent radiologist who was blinded to clinical data, CT interpretation, and EP FOCUS performed retrospective measures of the proximal aorta within 4 cm of the aortic valve.

  • Inclusion Criteria: Patients older than 18 years and who were treated at 1 of 3 affiliated EDs within a month preceding diagnosis for a visit attributed to AAD or during the same hospital visit.

  • Exclusion Criteria: Patients were excluded if they were transferred from an outside hospital with a known diagnosis of AAD, if they had a history of acute trauma, if they were not treated in the ED, if they had a descending aortic dissection (distal to the left subclavian artery), or if they were treated at an outside hospital. Additionally, patients were excluded if medical record review did not support the patient having a diagnosis of AAD. Mortality differences were adjusted by excluding patients with a DNR order.

  • Primary Endpoint: time to diagnosis - the difference between the time being roomed in an ED treatment area (acknowledged by time stamp in the EHR) to diagnosis of AAD made by advanced imaging (CTA, magnetic resonance imaging, transesophageal echocardiography).

  • Secondary Endpoints:

    • Time to disposition

    • Misdiagnosis rate (admitted/discharged with a diagnosis other than AAD)

    • Adjusted mortality differences between cohorts

Results: 32 patients were identified through EHR review and autopsy reports. 16 patients identified into each cohort group (FOCUS and non-EP FOCUS).

  • Median time to diagnosis was significantly faster in the FOCUS group at 80 minutes, with 226 minutes to diagnosis in the non-FOCUS group (p = 0.023)

  • Almost 94% of cases of AAD in the study population were found by advanced imaging to have a proximal aortic diameter greater than 4 cm at the time of diagnosis

    • Mean aortic size was found to be 5.45 cm in the FOCUS group and 5.44 in the non-FOCUS group (p = 0.98)

  • There was no significant difference in time to disposition between the two cohorts: 134 minutes in the FOCUS group vs. 205 minutes in the non-FOCUS group (p = 0.27)

  • Rate of misdiagnosis was statistically significant between the FOCUS group and the non-FOCUS group: 0% in the FOCUS group and 43.8% in the non-FOCUS group (p = 0.028)

  • Adjusted mortality percentage was 15.4% in the FOCUS group and 37.5% in the non-FOCUS group, however was not statistically significant (p = 0.24)

Takeaway: EP FOCUS enabled quicker diagnosis of AAD and reduced the potential of misdiagnosis when compared to those who did not undergo EP FOCUS. Because the mortality of AAD is directly related to time, one could conclude that using FOCUS can improve mortality from AAD, yet this particular study did not support that idea. There was a trend that did show patients to have quicker time to disposition when EP FOCUS was utilized, however this was not statistically significant. Limitations include potential for selection bias when deciding whether to utilize FOCUS in the case of a potential AAD, inadequate powering of the study to answer secondary outcome measures, and a possible number of patients who did not have an autopsy performed. In summary, because FOCUS is a fast, non-invasive, non-expensive tool that can possibly reduce the amount of time taken to diagnose AAD, it is encouraged to be utilized for patients with symptoms suggestive of aortic dissection.