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Date: April 12th, 2018

Reference: Ohle R et al. Clinical Examination for Acute Aortic Dissection: A Systematic Review and Meta-analysis. AEM April 2018

Guest Skeptic: Dr. Corey Heitz is an emergency physician in Roanoke, Virginia. He is also the CME editor for Academic Emergency Medicine (AEM).

Case: You are in the emergency department caring for a 65-year-old man with sharp chest pain radiating to the back. Blood pressure is elevated, and his pain was sudden in onset. His chest x-ray is normal, and there is no sign of asymmetric pulses. The EKG and laboratory tests are normal. You are wondering if you need to order a CT to rule out an aortic dissection.

Background: Aortic dissection is a rare but deadly disease which can confound the emergency physician’s diagnostic abilities. Some estimates are that up to 38% of cases are initially missed [1]. Mortality is up to 40% in the acute phase [2] , and 70% by two weeks [3].

The most common feature of aortic dissection is pain, in the chest, back, and/or abdomen, but with aortic dissection being so rare and pain being so prevalent a complaint, diagnosing aortic dissection becomes difficult. Data is lacking on predictive value of clinical features; much of the prior literature focuses on patients already diagnosed with aortic dissection.

There are two clinical prediction tools for the diagnosis of aortic dissection. One is from the American Heart Association called the aortic dissection detection (ADD) risk score. Our good friend over at REBEL EM, Salim Rezaie put together a nice table showing the score that we will include in the show notes. If any one of the predisposing conditions, pain features or physical exam findings are positive you add one point to the score.

The other is a simpler three-variable rule called the Von Kodolitsch score. This tool includes aortic pain (immediate-onset tearing or ripping pain), mediastinal/aortic widening on chest x-ray, or pulse/BP differential.

American College of Emergency Physicians (ACEP) published a guideline in 2015 for the diagnosis of acute aortic dissection. ACEP gives level C recommendations for the use of existing clinical decision tools:

  • “In an attempt to identify patients at very low risk for acute non-traumatic thoracic aortic dissection, do not use existing clinical decision rules alone. The decision to pursue further workup for acute non-traumatic aortic dissection should be at the discretion of the treating physician.” [4]

Clinical Question: What is the diagnostic accuracy in aortic dissection of various clinical features (history and physical), imaging tests and clinical decision instruments?

Reference: Ohle R et al. Clinical Examination for Acute Aortic Dissection: A Systematic Review and Meta-analysis. AEM April 2018

  • Population: Adult patients presenting to the emergency department with suspected acute aortic dissection in whom testing, criterion standard, and results of testing were available,
  • Intervention: This was a review of diagnostic accuracy in aortic dissection, so no interventions were performed.
  • Comparison: None
  • Outcome: Diagnostic accuracy of various tests, features of aortic dissection and clinical decision instruments (sensitivity, specificity and likelihood ratios).

Dr. Robert Ohle

This is an SGEMHOP episode. We are pleased to welcome the lead author of this SRMA, Dr. Robert Ohle. Robert is a practicing emergency medicine physician and Director of Research for emergency medicine at Health Science North in Sudbury, Ontario. His research program focuses on improving recognition and reducing time to treatment of acute aortic dissection. He is currently working on Canadian practice guidelines for the diagnosis of acute aortic dissection in the emergency department.

Authors’ Conclusions: “Suspicion for acute aortic dissection should be raised with hypotension, pulse, or neurologic deficit. Conversely, a low AHA ADD score decreases suspicion. Clinical gestalt informed by high- and low-risk features together with an absence of an alternative diagnosis should drive investigation for acute aortic dissection.”

Quality Checklist for Systematic Review Diagnostic Studies:

  1. The diagnostic question is clinically relevant with an established criterion standard. Yes
  2. The search for studies was detailed and exhaustive. Yes
  3. The methodological quality of primary studies were assessed for common forms of diagnostic research bias. Yes
  4. The assessment of studies were reproducible. Yes
  5. There was low heterogeneity for estimates of sensitivity or specificity. No
  6. The summary diagnostic accuracy is sufficiently precise to improve upon existing clinical decision-making models. No

Key Results: From the search, 792 abstracts and articles were found, and 60 met the eligibility criteria. Nine studies were included in the review. The overall quality was considered acceptable but there was moderate to high heterogeneity.

No individual risk factors, historical features, physical exam findings or basic investigations can rule in or out aortic dissection. Clinical decision instruments show some potential in improving diagnostic accuracy but are not ready for prime time.

  • Risk Factors:
    • History of Hypertension: LR+ 1-1.53 (I2 47%), LR- 0.61-1 (I2 84%)
    • Diabetes: LR+ 0.13-0.69 (I2 48%)
    • Connective Tissue Disease: LR+ 0.09-16.54 (I2 84%), LR- 1.11
    • Ischemic Heart Disease: LR+ 1.29 (95% CI = 1.14–1.45), LR– 0.39 (95% CI = 0.18–0.88)
  • Historical Features:
    • Syncope: LR+ 1–2.4 (I2 35%)
    • Severe Pain: LR+ 1.47–2.29 (I2 95%), LR– 0.31–0.68 (I2 90%)
    • Acute Onset: LR+ 1.01–2.60 (I2 95%), LR– 0.30–0.98 (I2 95%)
    • Back Pain: LR+ 1.04–23.14 (I2 95%), LR– 0.64–0.99
    • Tearing/Ripping: LR+ 0.85-10.76 (I2 89%), LR- 0.41-1.26 (I2 34%)
  • Physical Examination:
    • Focal Neurologic Deficits: LR+ 4.34 (95% CI 3.33–5.65)
    • Pulse Deficit: LR+ 2.48 (95% CI 1.51–4.09)
    • Hypotension: LR+ 1.2–4.3 (I2 = 42%)
    • BP Differential Alone: No studies
    • Pulse differential: Sensitivity 21%-49%, specificity 82%–95%
  • Basic Investigations:
    • Mediastinum <8cm: LR– 0.136–0.600 (I2 93% )
    • WBCs >15,000 cells/ml: LR+ 0.37 (95% CI 0.20–0.68)
    • Ischemic Changes on ECG LR+ 1.03 (95% CI 0.29-3.63)
  • Clinical Decision Tools:
    • Von Kodolitsch score 0: LR– 0.07 (95% CI 0.06–0.09 )
    • Von Kodolitsch score 3: LR+ 65.79 (95% CI 4.08–1061.4)
    • AHA ADD risk score = 0: LR– of 0.22 (95% CI 0.15–0.33)
    • AHA ADD risk score >1: LR+ 2.29 (95% CI 1.83–2.86)

Listen to the podcast on iTunes to hear Robert’s responses to our five nerdy questions.

1) Search-  You did a great search. It was interesting to see that four of the nine articles included weren’t found on your initial search, but by reviewing references of the ones that were. This emphasizes the importance of not just doing an electronic database search but also having a research librarian, hand searching references and looking for the grey literature. Do you think there may have been other missed studies?

2) Heterogeneity – The heterogeneity on some of the was moderate to high. Can you explain heterogeneity briefly to the SGEMers and comment on how do you think this should impact our interpretation of the results.?

3) Partial Verification Bias – The prevalence of aortic dissection in the included papers ranged from 22% to 76%. These numbers seem higher than clinical practice would tell us when patients present to the emergency department with “undifferentiated chest pain”. This suggests partial verification bias. Can you explain partial verification bias to the SGEMers and how it could impact the sensitivity and specificity? Also, can you comment on how we can apply this in practice considering the bias?

4) D-Dimer – This is an elephant in the room. You did not investigate the diagnostic accuracy of the d-dimer for aortic dissection. Can you explain why you did not address this issue and also summarize your thoughts on the use of the d-dimer?

5) Clinical Decision Tools – You looked at two clinical decision tools (AHA ADD risk score and the Von Kodolitsch score). ACEP guidelines only give a C recommendation for using clinical decision instruments for the diagnosis of aortic dissection. However, a Von Kodolistch score has a LR- of 0.07 (95% CI 0.06-0.09) which could be considered good enough to rule-out the condition. Would you recommend using the Von Kodolistch scoring system?

Do you have anything else you would like to tell the SGEMers about your study? Listen to the podcast on iTunes to hear Robert’s response.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We generally agree with the authors’ conclusions.

SGEM Bottom Line: Diagnosing aortic dissection in an undifferentiated population presenting to the emergency department continues to be a diagnostic challenge.

Case Resolution: The patient’s pain persists, and in fact worsens despite medical treatment in the emergency department. You elect to perform a CT angiogram, and diagnose him with a descending aortic dissection.

Dr. Corey Heitz

Clinical Application: We do not have strong evidence to guide our care in these patients. Various clinical data can increase and decrease the likelihood of an aortic dissection but not rule it in or out. It will take a combination of a good history, followed by a directed physical exam, basic investigations, clinical gestalt and shared decision making on how best to proceed. These decisions will all take place in a context that will depend on many factors (patient, physician and resources, medical-legal environment, etc).

What Do I Tell the Patient? Well, prior to the CT, I tell my patient that his studies looking at acute coronary abnormalities are normal, but his pain is concerning for aortic dissection, or a tear in the big blood vessel coming from his heart. I would like to perform a CT scan to rule out this life-threatening condition.

Keener Kontest: Last weeks’ winner was Dr. Ryker Kiel a R1 from Beaumont Hospital in Michigan. Commander Ryker knew ergotmine was contraindicated in patient with a history of vascular disease (including hypertension) and carboprost is contraindicated in patients with a history of asthma.

Listen to the SGEM podcast on iTunes to hear this weeks’ question. If you know the answer send an email to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Other FOAMed:

  • Life in the Fast Lane: Aortic Dissection
  • EM Cases: Aortic Dissection
  • First10EM: D-dimer and Aortic Dissections
  • REBEL EM: The ADVISED Trial – A novel clinical algorithm for the diagnosis of acute aortic syndromes
  • St. Emlyns: The Time Bomb of Doom What I Think About When I’m Tending Broad Beans
  • BroomeDocs: Gamblers and Dissection – A Music Treat.

SGEMHOP: Now it is your turn SGEMers. What do you think of this episode? Tweet your comments using #SGEMHOP. What questions do you have for Robert and his team? Ask them on the SGEM blog. The best social media feedback will be published in AEM.

Also, don’t forget those of you who are subscribers to Academic Emergency Medicine can head over to the AEM home page to get CME credit for this podcast and article. We will put the process on the SGEM blog:

  • Go to the Wiley Health Learning website
  • Register and create a log in
  • Search for Academic Emergency Medicine – “April”
  • Complete the five questions and submit your answers
  • Please email Corey (coreyheitzmd@gmail.com) with any questions or difficulties.

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

References:

  1. Spittell PC, Spittell Jr JA, Joyce JW.  et al.  Clinical features and differential diagnosis of aortic dissection: experience with 236 cases (1980 through 1990).  Mayo Clin Proc.1993;68:642-651.
  2. Hirst AE Jr, Johns VJ Jr, Kime SW Jr. Dissecting aneurysm of the aorta: a review of 505 cases. Medicine 1958;37:217–79.
  3. Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000;283:897– 903.
  4. Diercks DB, Promes SB, Schuur JD, Shah K, Valente JH, Cantrill SV. Clinical policy: critical issues in the evalua- tion and management of adult patients with suspected acute nontraumatic thoracic aortic dissection. Ann Emerg Med 2015;65(32–42):e12.