Ep 114 Pulmonary Embolism Challenges in Diagnosis 2 – Imaging, Pregnancy, Subsegmental PE

In Part 1 of Pulmonary Embolism Challenges in Diagnosis Drs. Helman, Lang and DeWit discussed a workup algorithm using PERC and Wells score, the bleeding risk of treated pulmonary embolism, pearls in decision making on whether or not to work up a patient for pulmonary embolism, how risk factors contribute to pretest probability, the YEARS criteria and age-adjusted D-dimer. In this Part 2 we answer questions such as: what are the important test characteristics of CTPA we need to understand? Which patients with subsegmental pulmonary embolism should we treat? When should we consider VQ SPECT? What is the best algorithm for the work up of pulmonary embolism in pregnant patients? How best should we implement pulmonary embolism diagnostic decision tools in your ED? and many more…

Podcast production, sound design & editing by Anton Helman, additional editing by Sucheta Sinha

Written Summary and blog post by Shaun Mehta & Alexander Hart, edited by Anton Helman August 2018

 

CTPA test characteristics and pulmonary embolism diagnosis

As with the rest of emergency medicine, our interventions are rarely benign. In order to avoid unnecessary radiation and major bleeding complications as a result of anticoagulating patients with false positive CTPA results, it’s important to have a rational approach to imaging for PEs as well as a good approach to shared decision making with our colleagues, our radiologists and our patients.

Although CTPA has become the gold standard for diagnosing PE and remains the best imaging modality available, it is far from perfect. The CTPA is prone to over-diagnosing clinically irrelevant emboli in low-risk patients [1]. Furthermore, although its sensitivity approaches 100% for clinically relevant PEs, in those with high pre-test possibility there is a small chance a clot might be missed. Those patients at high risk for PE based on a Wells score >6 with a negative CTPA should be counseled that although the present CTPA does not show a PE, up to 5% of high risk patients may develop a PE within a few months of a negative CTPA [2,3].

What about clot burden and location? These imaging characteristics have not been shown to accurately predict outcome, or even symptoms. The clinical context is much more important, and markers such as hypotension and hypoxia are better predictors of outcome [4].

Subsegmental pulmonary embolism: To treat or not to treat?

In the last 10 years, the incidence of diagnosed PE has doubled, despite no change in mortality, partly due to advances in CT technology and partly due to radiologists overcalling subsegmental PEs due to medico-legal concerns. With modern CTs, subsegmental PEs are more often diagnosed. Although there is some variability in practice, most emergency physicians end up treating subsegmental PEs. But should we?

An observational study by Goy et al. in 2015 reviewed 2213 patients with a diagnosis of subsegmental PE, and showed that whether or not anticoagulation was given, there were no recurrent PEs, yet 5% of anticoagulated patients developed life-threatening bleeding [5]. Other studies have yielded similar results [6].

Shared decision-making. Consider the patient’s bleeding risk (HASBLED score) and discuss potential treatment options. The 2018 ACEP Clinical Policy on Acute Venous Thromboembolic Disease gives withholding anticoagulation in patients with subsegmental PE a Level C recommendation and states: “Given the lack of evidence, anticoagulation treatment decisions for patients with subsegmental PE without associated DVT should be guided by individual patient risk profiles and preferences [Consensus recommendation].”

emergency management of pediatric seizures

Start anticoagulation for subsegmental PE in the ED with an expectation that anticoagulation may be stopped in follow-up. While the risk of major bleeding with a full course of anticoagulation is significant, the risk of bleeding with a few doses of anticoagulant is very low. Thus, starting treatment for subsegmental PE in the ED and referring the patient for early timely follow up in a thrombosis or internal medicine clinic (within a few days) is a reasonable option. Counseling your patient that the consultant may recommend stopping the anticoagulant is essential to avoid conflicting messages. Consultants may risk stratify low risk patients with serial leg dopplers to direct ongoing therapy.

V/Q Scan in pulmonary embolism challenges in diagnosis

Many emergency physicians are comfortable using D-dimers, dopplers and CTPA, but often forget about the value of V/Q scans [8]. Consider this test in:

  • Young, otherwise healthy patients with a normal chest x-ray
  • CT contrast allergy

V/Q SPECT

V/Q SPECT has been shown to have superior accuracy compared to traditional V/Q and has similar sensitivity, but poorer specificity compared to CTPA for pulmonary embolism [9]. V/Q SPECT eliminates intermediate probability scans, and is reported dichotomously as positive or negative for PE. This avoids the ambiguity of results in traditional V/Q. Robust data is pending regarding its diagnostic utility compared to CTPA.

Pregnancy and pulmonary embolism challenges in diagnosis

There are many proposed strategies for working up the pregnant patient for PE, but no diagnostic algorithm has robust enough evidence for strong recommendations [10,11,12]. Pregnant women have generally been excluded from the studies that have provided support for the use of clinical prediction tools and D-dimer in the diagnosis of pulmonary embolism.

Although a trimester-adjusted D-dimer (cutoffs increase by 250 for each trimester) has been suggested for PE in pregnancy, it is not recommended by our experts. While the DiPEP study could not find a D-dimer threshold below which PE could be ruled out in pregnancy [13], there is some observational evidence that a negative D-dimer result rules out PE in otherwise low-risk pregnant patients. A retrospective review of 152 pregnant and post-partum patients who underwent V/Q or CTPA for suspected PE found a sensitivity of 100%  but only a specificity of 42% [14]. The American Thoracic Society recommends not using D-dimer in pregnancy [15].

The European Society of Cardiology recommends considering V/Q scan to rule out suspected PE in pregnant women with normal CXR (Class IIB recommendation) and that CTPA should be considered if the CXR is abnormal or if V/Q scan is not readily available (Class IIa recommendation) [16].

Our experts recommend starting with two-tier Wells and PERC, an unadjusted D-dimer if necessary, then moving onto bilateral leg dopplers, and then considering chest imaging based on the CADTH Optimal Strategies for the Diagnosis of Acute Pulmonary Embolism 2018 Recommendations [17].

  1. Two-tier Wells
  2. PERC
  3. D-dimer
  4. Leg ultrasound
  5. CTPA or VQ SPECT

 

pulmonary embolism challenges in diagnosis

From CADTH Optimal Strategies for the Diagnosis of Acute Pulmonary Embolism: Recommendations 2018

Can leg dopplers rule PE in or out? Ultrasound shows a DVT in up to 30-50% of patients with PE, and finding a proximal DVT in patients suspected of having PE is considered sufficient to warrant anticoagulation without further testing [18]. A negative Doppler ultrasound for DVT does not rule out a PE.

Radiation Risk in pregnancy: CTPA vs. V/Q

A CTPA transmits more radiation to the maternal breast tissue, whereas a V/Q scan transmits more radiation to the fetus. There is no hard data here to guide practice and specific strategies remain controversial. However, it is important to realize that both VQ and CTPA fetal radiation dose falls well below teratogenic doses. In the ED, discuss radiation risk with your patient and the radiologist on-call to determine the best imaging modality.

Departmental pulmonary embolism decision support

Our experts encourage every ED to develop a protocol for PE diagnosis to maintain consistency and promote institutional support for clinicians. If implemented thoughtfully with input from the physician group, this practice could lead to reduced imaging rates and increased diagnostic yield [19]. However, changing ED culture may be challenging, and results depend on the point of implementation to affect diagnostic momentum.

pulmonary embolism pregnancy algorithm

References

  1. Writing Group for the Christopher Study Investigators. Effectiveness of Managing Suspected Pulmonary Embolism Using an Algorithm Combining Clinical Probability, D-Dimer Testing, and Computed Tomography. JAMA. 2006;295(2):172-179.
  2. van der Hulle T, van Es N, den Exter PL, et al. Is a normal computed tomography pulmonary angiography safe to rule out acute pulmonary embolism in patients with a likely clinical probability? A patient-level meta-analysis. Thromb Haemost. 2017;117(8):1622-1629.
  3. Outcomes following a negative computed tomography pulmonary angiography according to pulmonary embolism prevalence: a meta-analysis of the management outcome studies.  J Thromb Haemost. 2018 Jun;16(6):1107-1120.
  4. Den exter PL, Van es J, Klok FA, et al. Risk profile and clinical outcome of symptomatic subsegmental acute pulmonary embolism. Blood. 2013;122(7):1144-1150.
  5. Goy J, Lee J, Levine O, Chaudhry S, Crowther M. Sub-segmental pulmonary embolism in three academic teaching hospitals: a review of management and outcomes. J Thromb Haemost. 2015;13(2):214-8.
  6. Yoo HH, Queluz TH, El dib R. Anticoagulant treatment for subsegmental pulmonary embolism. Cochrane Database Syst Rev. 2014;(4):CD010222.
  7. ACEP Clinical Policies Subcommittee. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department with Suspected Acute Venous Thromboembolic Disease. Ann Emerg Med 2018; 71(5): e59-109.
  8. Le Roux PY, Pelletier-Galarneau M, De Laroche R, Hofman MS, Zuckier LS, Roach P, et al. Pulmonary scintigraphy for the diagnosis of acute pulmonary embolism: a survey of current practices in Australia, Canada, and France. J Nucl Med. 2016;56(8):1212-7.
  9. Gutte H, Mortensen J, Jensen CV, et al. Comparison of V/Q SPECT and planar V/Q lung scintigraphy in diagnosing acute pulmonary embolism. Nucl Med Commun. 2010;31(1):82-6.
  10. Kline JA, Williams GW, Hernandez-nino J. D-dimer concentrations in normal pregnancy: new diagnostic thresholds are needed. Clin Chem. 2005;51(5):825-9.
  11. Hunt BJ, Parmar K, Horspool K, et al. The DiPEP (Diagnosis of PE in Pregnancy) biomarker study: An observational cohort study augmented with additional cases to determine the diagnostic utility of biomarkers for suspected venous thromboembolism during pregnancy and puerperium. Br J Haematol. 2018;180(5):694-704.
  12. Leung AN, Bull TM, Jaeschke R, Lockwood CJ, Boiselle PM. Evaluation of Suspected Pulmonary Embolism in Pregnancy. American Journal of Respiratory Critical Care Medicine 2011; 184: 1200-1208.
  13. Hunt BJ, Parmar K, Horspool K, et al. The DiPEP (Diagnosis of PE in Pregnancy) biomarker study: An observational cohort study augmented with additional cases to determine the diagnostic utility of biomarkers for suspected venous thromboembolism during pregnancy and puerperium. Br J Haematol. 2018;180(5):694-704.
  14. Choi H, Krishnamoorthy D. The diagnostic utility of D-dimer and other clinical variables in pregnant and post-partum patients with suspected acute pulmonary embolism. Int J Emerg Med. 2018;11(1):10.
  15. Leung AN, Bull TM, Jaeschke R, et al. American Thoracic Society documents: an official American Thoracic Society/Society of Thoracic Radiology Clinical Practice Guideline–Evaluation of Suspected Pulmonary Embolism in Pregnancy. Radiology. 2012;262(2):635-46.
  16. Konstantinides S, Torbicki A, Agnelli G, et al. 2014 ESC guidelines on the diagnosis and management of acute pulmonary embolism. Eur Heart J. 2014;35(43):3033-69, 3069a-3069k.
  17. Optimal Strategies for the Diagnosis of Acute Pulmonary Embolism: Recommendations. Ottawa: CADTH; 2018 Mar. (CADTH optimal use report; vol.6, no.3c).
  18. Le Gal G, Righini M, Sanchez O, et al. A positive compression ultrasonography of the lower limb veins is highly predictive of pulmonary embolism on computed tomography in suspected patients. Thromb Haemost. 2006;95(6):963-6.
  19. Deblois S, Chartrand-lefebvre C, Toporowicz K, Chen Z, Lepanto L. Interventions to Reduce the Overuse of Imaging for Pulmonary Embolism: A Systematic Review. J Hosp Med. 2018;13(1):52-61.
  1. Additional Podcast References  
    1. Van Mens TE, Scheres LJ, De jong PG, Leeflang MM, Nijkeuter M, Middeldorp S. Imaging for the exclusion of pulmonary embolism in pregnancy. Cochrane Database Syst Rev. 2017;1:CD011053.
    2. Van der, Mairuhu A, Tromeur C, Couturaud F, Huisman M, Klok F. Use of clinical prediction rules and D-dimer tests in the diagnostic management of pregnant patients with suspected acute pulmonary embolism. Blood Rev. 2017;31(2):31-36.
    3. Lin MP, Probst MA, Puskarich MA, et al. Improving perceptions of empathy in patients undergoing low-yield computerized tomographic imaging in the emergency department. Patient Educ Couns. 2018;101(4):717-722.
    4. Kline JA, Neumann D, Raad S, et al. Impact of Patient Affect on Physician Estimate of Probability of Serious Illness and Test Ordering. Acad Med. 2017;92(11):1607-1616.

Other FOAMed Resources on PE imaging, subsegmental, and PE in pregnancy

EP Monthly on CTPA – Is this test just a little too good?

EM Literature of Note on Again with the failings of CTPA

Rebel EM on The DiPEP study

EM Docs on Controversies in imaging and treatment of subsegmental PE

Rebel EM on ACEP Clinical Policy on Acute VTE 2018

Drs. Helman and Lang have no conflicts of interest to declare. Dr. DeWit conducts research funded by Bayer. 

Now Test Your Knowledge:

1. A 80 year-old woman presents to your ED with new pleuritic chest pain and dyspnea. She has no personal and family history of venous thromboembolism, no recent immobilization, no active cancer or exogenous estrogen use. You decide to order a CTPA and a PE is diagnosed. What percentage of patients diagnosed with PE have no risk factors?

A. 30%

B. 50%

C. 10%

D. 70%

Answer: B

The important risk factors to consider in assessing pretest probability include personal and family history of venous thromboembolism, recent immobilization, active cancer and exogenous estrogen use. It is important to realize that up to 50% of PEs are diagnosed in patients with no apparent risk factor.

2. Which of the following chief complaints would make you most concerned for a diagnosis for pulmonary embolism?

A. Chest pain

B. Exertional dyspnea

C. Chronic fatigue

D. Anorexia

Answer: B

True exertional dyspnea is a common presentation for PE. Another common symptom is new onset fatigue, especially in the dyspneic patient who tells you that they developed unusual fatigue that coincides with their dyspnea. Although patients with chest pain should be considered for PE, chest pain is probably less common than we have traditionally thought. , fever and pleuritic chest pain.

3. What signs on an ECG make you most concerned for a pulmonary embolism?

A. S1Q3T3

B. old RBBB

C. flipped T waves in anterior and inferior leads

D. sinus bradycardia

Answer: C

Signs of PE on ECG include sinus tachycardia, RV strain pattern, incomplete RBBB, S1Q3T3, dominant R wave in V1, ST-segment elevation in V1 and aVR and low voltages. The most specific ECG finding in PE is flipped T waves in anterior AND inferior leads. S1Q3T3 has a poor specificity for PE.

4. A 70-year old gentleman presents to your ED with pleuritic chest pain and dyspnea. His vital signs are: HR 110, BP 140/90, SpO2 94% on RA, RR 22, T 37. His right leg is swollen compared to his left. He denies any hemoptysis, any recent surgery or immobilization, any history of malignancy or previous venous thromboembolic disease. What is your next step?

A. Consider a CTPA

B. Send a D-dimer

C. Use PERC

D. Anticoagulate him

Answer: A
Our experts suggest an Algorithmic Approach: Once you have decided to test for PE, our experts suggest starting with Wells to get an idea of the pre-test probability.
1.     If <2, use PERC
2.     If 2-4, send D-dimer
3.     If >4, consider a CTPA
This patient’s Well’s score is 4.5. Therefore consider ordering a CTPA.

5. A 30-year old woman presents to your ED with pleuritic chest pain and dyspnea. At triage, her vital signs are: HR 110, BP 140/90, SpO2 94% on RA, RR 22, T 37. She has no clinical signs of DVT, she denies hemoptysis, any recent surgery or immobilization, and denies any history of malignancy or previous venous thromboembolic disease. What is your next step?

A. Consider a CTPA

B. Send a D-dimer

C. Use PERC

D. Anticoagulate him

Answer: C

Our experts suggest an Algorithmic Approach:

Once you have decided to test for PE, our experts suggest starting with Wells to get an idea of the pre-test probability.

  1. If <2, use PERC
  2. If 2-4, send D-dimer
  3. If >4, consider a CTPA

This patient’s Well’s score is 1.5. Therefore consider using the PERC rule.

6. A 60-year old woman presents to your ED with pleuritic chest pain and hemoptysis. Her vital signs are: HR 110, BP 140/90, SpO2 94% on RA, RR 22, T 37. She has no clinical signs of DVT, she denies any recent surgery or immobilization, and denies any history of malignancy or previous venous thromboembolic disease. When you assess her, her HR has normalized to 90 bpm. What is your next step?

A. Consider a CTPA

B. Send a D-dimer

C. Use PERC

D. Anticoagulate him

Answer: B

Triage tachycardia that normalizes by the time the patient is assessed by the ED physician, should be considered tachycardia when using the Wells score.

Our experts suggest an Algorithmic Approach:

Once you have decided to test for PE, our experts suggest starting with Wells to get an idea of the pre-test probability.

  1. If <2, use PERC
  2. If 2-4, send D-dimer
  3. If >4, consider a CTPA

This patient’s Well’s score is 2.5. Therefore consider ordering a D-dimer. You can apply the Age-adjusted D-dimer. The evidence is reasonably convincing for the use of age-adjusted D-dimer and is recommended by our experts. ACEP suggests that using an age-adjusted approach may reduce the need for advanced imaging without significantly increasing missed cases of PE.

7. You have just diagnosed bilateral subsegmental PEs in your dyspneic patient without any other features of PE in the ED. Their HAS-BLED score is 0. What is the most reasonable next step?

A. Start anticoagulation and counsel the patient they will need this for at least 3 months

B. Start anticoagulation and counsel the patient to follow-up in an internal medicine or thrombosis clinic and that their therapy may be stopped in a few days.

C. You do not need to treat their subsegmental PEs because they are always benign.

D. Their HAS-BLED score is too high and their risk of serious bleed outweighs the risk of mortality from PE. You do not anticoagulate them.

Answer: B

Our experts suggest to start anticoagulation for subsegmental PE in the ED with an expectation that anticoagulation may be stopped in follow-up. While evidence suggests that untreated subsegmental PEs rarely result in significant morbidity or mortality, the risk of bleeding with a few doses of anticoagulant is very low. Thus, starting treatment for subsegmental PE in the ED and referring the patient for early timely follow up in a thrombosis or internal medicine clinic (within a few days) is a reasonable option. Counseling your patient that the consultant may recommend stopping the anticoagulant is essential to avoid conflicting messages. Consultants may risk stratify low risk patients with serial leg dopplers to direct ongoing therapy.

8. A 25-year old female, 30 weeks pregnant, presents to your ED with new pleuritic chest pain and dyspnea. You consider the diagnosis of PE. What is your next step?

A. Start with a two-tier Wells and PERC

B. Order a D-dimer

C. V/Q scan

D. Anticoagulate immediately as she is symptomatic

Answer: A

Our experts recommend starting with two-tier Wells and PERC, an unadjusted D-dimer if necessary, then moving onto bilateral leg dopplers, and then considering chest imaging based on the CADTH Optimal Strategies for the Diagnosis of Acute Pulmonary Embolism 2018 Recommendations.

Two Tier Model

–  Patient risk is determined to be “PE Unlikely” (0-4 points, 12.1% incidence of PE) or “PE Likely” (>4 points, 37.1% incidence of PE): consider CTPA

9. Which of the following statements is true regarding pulmonary embolism in a pregnant patient?

A. CTPA transmits more radiation to the fetus, whereas a V/Q scan transmits more radiation to the maternal breast tissue

B. Radiation dose from VQ and CTPA both fall well below teratogenic doses

C. Negative doppler ultrasound bilaterally in a pregnant patient sufficiently rules out a PE

D. There is strong evidence that PE can be ruled out in pregnancy with D-dimer

Answer: B

– A CTPA transmits more radiation to the maternal breast tissue, whereas a V/Q scan transmits more radiation to the fetus.

A negative Doppler ultrasound for DVT does not rule out a PE.

– The DiPEP study could not find a D-dimer threshold below which PE could be ruled out in pregnancy. However, there is some observational evidence that a negative D-dimer result rules out PE in otherwise low-risk pregnant patients.

10. Which of the following statements regarding chest X-ray in the work up of PE is CORRECT?

A. The main role of chest X-ray in the work up of PE is to confirm your suspicion while the patient is waiting for CTPA or V/Q scan

B. Westermark and Hampton’s Hump are commonly seen in chest X-rays of patients with PE

C. Pulmonary infarct from PE can be confused with an infiltrate from pneumonia on chest X-ray

D. Pleural effusion should not be seen on the chest X-ray of a patient with PE

Answer: C

The main role of a chest X-ray is to rule out alternative diagnoses. Beware of diagnosing pneumonia based on an infiltrate, as a pulmonary infarct from PE can look similar. The chest X-ray is often normal in PE. The classic findings are raised hemidiaphragm, pleural effusion, Westermark’s sign and Hampton’s hump. The latter are usually identified in retrospect after the diagnosis of PE has already been made.

11. You have just diagnosed a PE in  a young, active male patient in the ED who presented with mild pleuritic chest pain. They have no other comorbidities and have no bleeding risks. Their vital signs are: T37, HR 100, BP 140/90, SpO2 95% on RA, RR 20. On bedside ultrasound you note signs of right heart strain. What is the most reasonable disposition for this patient?

A. Admit the patient.

B. Start anticoagulation and follow-up in thrombosis clinic.

C. Monitor in the ED for 6 hours at least.

D. Start anticoagulation and follow-up with family physician in 2-4 weeks.

Answer: B

POCUS can be helpful in the arrest or peri-arrest patient who are not safe to leave the ED to get a CTPA. Our experts do not recommend using POCUS to aid in disposition decisions. Even if sonographic signs of right heart strain are present, PE can still be managed as an outpatient if HESTIA criteria for outpatient management are fulfilled.

HESTIA criteria on MD Calc https://www.mdcalc.com/hestia-criteria-outpatient-pulmonary-embolism-treatment

12. All of the following are common pitfalls in the diagnosis of PE, except:

A. Failure to consider the diagnosis of PE in patients with comorbidities

B. Underestimating the risk of PE

C. Misinterpretation of vital signs

D. Assuming low risk for PE in patients with no apparent risk factors.

Answer: B

Overestimating the risk of PE is a common pitfall. The vast majority of patients who we are considering for PE diagnosis are low risk according to Well’s Criteria. We order many needless CTPAs, with their inherent problems of overdiagnosis and radiation risk, for fear of a PE in low risk and negligible risk patients.

13. A 35-year old pregnant female presents to your ED with right-sided calf swelling and new onset dyspnea. A Doppler ultrasound is positive for a proximal right-sided DVT in her leg. Your next step is?

A. Order CTPA to rule out PE.

B. Order a V/Q scan

C. Apply the Two Tier model

D. Anticoagulate the patient

Answer: D

Finding a proximal DVT in patients suspected of having PE is considered sufficient to warrant anticoagulation without further testing.

14. The following is TRUE about V/Q SPECT:

A. V/Q SPECT should not be considered in patients with contrast allergy

B. V/Q SPECT has poorer specificity than CTPA for PE

C. V/Q SPECT is reported as positive, negative, and intermediate probability

D. V/Q SPECT is more ambiguous than traditional V/Q

Answer: B

V/Q SPECT has been shown to have superior accuracy compared to traditional V/Q and has similar sensitivity, but poorer specificity compared to CTPA for PE. V/Q SPECT eliminates intermediate probability scans, and is reported as positive or negative for PE. This avoids the ambiguity of results in traditional V/Q.

15. You are seeing a patient in the ED whose Wells score is 7. You did a CTPA which was negative for PE. How do you counsel the patient?

A. They still have a 10% chance of a clinically relevant clot today.

B. They still have a 5% chance of clinically relevant clot today.

C. Due to their risk factors they need to return to the ED for repeat CTPA in 1 week.

D. Due to their risk factors there is a small chance they may develop a PE within a few months.

Answer: D

CTPA is gold standard for diagnosing PE but is far from perfect. CTPA is prone to over-diagnosing clinically irrelevant emboli in low-risk patients. Although its sensitivity approaches 100% for clinically relevant PEs, in those with high pre-test possibility there is a small chance a clot might be missed. If patients have a high risk for PE based on a Wells score >6 and a negative CTPA, they should be counseled that up to 5% of high risk patients may develop a PE within a few months.

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About the Author:

Dr. Anton Helman is an Emergency Physician at North York General in Toronto. He is an Assistant Professor at the University of Toronto, Division of Emergency Medicine and the Education Innovation Lead at the Schwartz-Reisman Emergency Medicine Instititute. He is the founder, editor-in-chief and host of Emergency Medicine Cases.

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