Really Focused or Hocus POCUS?

Chest pain byte

Echocardiography in the Evaluation of Chest Pain in the Emergency Department

Pol J Radiol Dec 2017 - Pubmed Link


Take Home Points

1. In a single center study riddled with limitations, a fairly comprehensive echo exam was specific for cardiac disease in patients with chest pain.

2. Based on this weak data, point of care echo is not sensitive enough to rule out serious cardiac causes of chest pain in the emergency department.


Background

Have you ever worked in an acute care setting? If not - you are missing out on a lot of people with chest pain. Suffice it to say, this is a common complaint and obviously the etiology of this pain ranges from incredibly benign to immediately life-threatening. Ultrasound is pretty good at finding a bunch of these serious causes (wall motion abnormalities in acute myocardial infarction, pulmonary embolism, pericardial effusion, cardiomyopathy, pneumonia) and can be somewhat helping in looking for others (aortic dissection). This is a similar concept to many studies that have been done in undifferentiated dyspnea. The idea in the present study is that we can apply a point of care ultrasound protocol to these patients with chest pain, especially focusing on ischemic causes and cardiomyopathies. If this is accurate, it might be able to help in the decision of who needs to be admitted to the hospital and who can be discharged with close follow up.


Questions

Can a focused echo protocol in the emergency department be used to determine cause of acute chest pain?

Can a focused echo protocol in the emergency department be used to determine the need for hospitalization?


Population

Study performed in single center in Saudi Arabia


Inclusion:

  • Presented to ED

  • Chest pain or other symptom concerning for MI

Exclusion:

  • None reported


Design

Prospective cohort, consecutive patients

Patients with chest pain received an echo by a blinded investigator

The results were used to determine diagnosis and disposition


Primary outcome was accuracy of ultrasound for final diagnosis based on stress test (if discharged) or diagnosis by admitting team using any subsequent imaging or testing (if admitted).


All patient got evaluation including:

  • History

  • Physical exam

  • ECG

  • Point of care transthoracic echo “immediately on arrival”


Divided into three groups of “risk for cardiac events” based on risk factors (family hx, HTN, dm, smoking, alcohol, diet, physical inactivity, obesity, OCPs, hormone replacement)

  • High risk (>3 risk factors)

  • Moderate risk (3 risk factors)

  • Low risk (<3 risk factors)


If everything negative → they were discharged and scheduled for follow up in 24-48 hrs. Determined if +stress or not.

If positive → admitted. Further testing confirmed or denied the diagnosis.


Who did the ultrasounds?

Single investigator (the sole author) who is from the Department of Radiology and Medical Imaging

Blinded to patients' status


The Scan

Phased array transducer

Phased


Their protocol:

4 cardiac views

Thoracic aorta

Upper abdominal aorta

IVC

Color doppler for shunting


Positive scan was:

  • Ischemic heart disease (abnormal wall motion, akinesis, hypokinesis in 2 different orientations, generalized hypokinesis with EF <40%)

  • Non-ischemic heart disease (asymmetrical septal hypertrophy, SAM, small LV cavity, septal immobility, premature closure of aortic valve). Left atrial volume >48mm, left atrial fractional shortening).

  • Mentions other findings but not clear if these were part of standard exam. Reversal of flow across MV and TV for restrictive CM? Focal Valve thickening for aortic stenosis? Aortic valve velocity and pericardial effusion also mentioned.


Obtaining Cardiac Windows - 5 Minute Sono

Cardiac Function - 5 Minute Sono

Aortic Dissection - 5 Minute Sono


Check out these great resources from our friends at The POCUS Atlas

The POCUS Atlas - Echo Pathology!

The POCUS Atlas - Evidence Atlas for Cardiac POCUS


Results

The Patients

250 patients over 2 years

  • Age 18-80 (mean 67)

  • 44% males

  • 65.2% were high risk (>3 risk factors)

  • 10.4% moderate risk (3)

  • 24.4% low risk (<3)


68% had positive echo findings

  • 86.5% of high risk

  • 7.6% of moderate risk

  • 5.9% low risk


Primary Outcome

Accuracy of Focused Echo for Cardiac Pathology (including Ischemic Heart Disease and Non-ischemic Heart Disease)

Sensitivity 85.86% (CI 80.21-90.39)

Specificity 100% (CI 93.15-100)

-LR 0.14

+LR ∞


Additional Findings

85% of positive studies in High risk were ischemic (22% acute MI, 62.6% angina), Hypertrophic cardiomyopathy was 8.2% of patients.

Moderate group - 15.4% (aka 2 patients) had acute myocardial infarction (AMI), smattering of other diagnoses

Low risk group - 1 patient had angina, 1 had AMI.


80 patients (32%) were discharged (all were high risk) → stress tests showed 35% (28 patients) had AMI, with ECG abnormal and elevated CK.


Limitations

Single center, single well trained operator.

External validity. This is outside of the US. The population seems different than typically described. There was a 79.2% prevalence of disease in this study. This high prevalence would certainly affect the accuracy of the results. Furthermore, many etiologies of chest pain were not even considered in their diagnostic pathway. It is not clear if anyone got a chest xray (or lung ultrasound). What about pneumonia, pneumothorax, pulmonary embolism, esophageal perforation, etc?).

Limited gold standard. How the accuracy was determined is not well described. We don’t know the exact confirmatory testing being done when the patients were admitted. We do know that if they were discharged, they just got a stress test, which is not always the best determination of acute coronary syndrome (not to mention using CK instead of troponin).


Discussion

Dangerous protocol? It seems, based on the information provided in the manuscript, that this study took all comers with the same symptoms, did the same work up and discharged home if it was negative. I would find it hard to believe this could actually be the case. Clearly, there needs to be an aspect of individualized care to the patient in front of you. There was deviation from the protocol, but it is only mentioned in the example of low risk patients who got early cardiac perfusion imaging and then a discharge instead of otherwise being admitted. There is no mention of patients getting admitted despite a normal (somewhat limited) work up. Remember that we always advocates for using ultrasound in conjunction with A) your brain and B) the rest of your diagnostic information (history, exam, and whatever other tests might be appropriate). I fear that this article is advocating for a more blindly binary use of POCUS - if positive → admit, if negative → discharge, instead of a more nuanced use of this modality as a helpful tool in your tool belt. I think that the unacceptably high rate of missed MI’s (for the United States anyway), is likely a result of this cookie-cutter protocol.


Take Home Points

1. In a single center study riddled with limitations, a fairly comprehensive echo exam was specific for cardiac disease in patients with chest pain.

2. Based on this weak data, point of care echo is not sensitive enough to rule out serious cardiac causes of chest pain in the emergency department.


Our score

2 Probes


Published on 06/18/18 06:00 AM
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