How accurate is EPSS in estimating ejection fraction?

Background

Bedside echocardiography has an established role in the time-sensitive assessment for pericardial effusion, relative chamber size, and global cardiac function of emergency department (ED) patients. Most ED physicians use visual estimation to gauge left ventricular ejection fraction (LVEF), a method that may be subject to inter-observer variability and inaccuracy (1). E-point septal separation (EPSS), the minimum separation between the anterior mitral valve leaflet and the interventricular septum, may offer a more objective measure of LVEF.

epss echo

EPSS was first studied in the 1970s as a quantitative, easily measured, and reproducible index of left ventricular function (2). In healthy individuals, the mitral valve leaflet reaches its maximum excursion near or at the septum during early diastole. EPSS increases as left ventricular ejection fraction (LVEF) decreases, and an EPSS of greater than 7mm predicts poor LVEF (3,4).

The gold standard for evaluating LVEF is a quantitative, calculated value obtained from comprehensive transthoracic echocardiography, which is impractical in the emergency department, thus EPSS offers a simple to learn and easy to obtain alternative, requiring only one view in the parasternal long axis. EPSS measurement is a technique feasible for the ED physician to perform at the bedside that can provide a convenient and reliable estimate of LVEF. 

 

E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction

Clinical Question

Does EPSS measurements obtained by ED physicians correlate with calculated LVEF from comprehensive transthoracic echocardiography (TTE)?

Can certain EPSS cutoff values be used to predict systolic dysfunction? 

What is the relationship between bedside visual estimates of global cardiac function (GCF) and the calculated LVEF measurements?

Methods & Study Design

• Design 

This was a prospective observational trial.

• Population 

A convenience sample of 80 hospitalized patients undergoing comprehensive TTE for any indication. Subjects were recruited between February and April 2012 from an academic level I trauma center. Exclusion criteria were known pregnancy or age less than 18 years.

• Intervention 

Three emergency ultrasound fellows performed bedside 4-view basic echocardiographic examinations consisting of subxiphoid, parasternal long, and parasternal short and apical views and made estimates of GCF. The fellows then obtained separate parasternal long-axis views and performed M-mode measurements of the EPSS. Comprehensive TTE was separately performed by cardiac sonographers and LVEF was calculated via the Teichholz method.

• Outcomes  

    • Subjective estimates of GCF categorized as normal systolic function (LVEF > 55%), moderate systolic dysfunction (30% > LVEF > 55%), or severe systolic dysfunction (LVEF < 30%)
    • EPSS measurements
    • Calculated LVEFs also categorized as normal/moderate/severe as above

Results

Calculated LVEF ranged from 13%-86%. EPSS ranged from 0.50-29.70 mm.

Men had higher EPSS scores and higher calculated estimates of LVEF. No other demographic or clinical variables were identified as potential covariates. 

The linear regression model revealed that EPSS is a statistically significant predictor (P < .001) of calculated LVEF.

An EPSS measurement of greater than 7 mm was 100% sensitive and 51.6% specific for severely reduced LVEF. An EPSS measurement of greater than 8 mm was 83.3% sensitive and 50.0% specific for any systolic dysfunction.

Estimated GCF and calculated LVEF were in agreement in 49 (69.0%) of subjects with a weighted Cohen κ of 0.58, with strongest agreement for subjects with severe systolic dysfunction.

epss echo

Strength & Limitations

Strengths:

This study is the first to demonstrate that EPSS can provide a quantitative prediction of LVEF. One strength of this study is the generalizability of the findings given that all indications for TTE were included. Another strength is that the ED ultrasound fellows and cardiac sonographers performed their studies independently, unlike a prior study that utilized the same scans performed by residents to obtain both EPSS and LVEF. 

Limitations:

There were possible misestimations of EPSS in certain pathologic states, such as overestimation of EPSS in mitral stenosis. Additionally, this paper describes the Teichholz method, which is subject to inaccuracies, especially in states of dyskinesis. Of note, the Teichholz method has since been supplanted by the modified Simpson’s rule and is no longer used clinically. On average, time from EPSS measurement to comprehensive echocardiogram was 6 hours with the possibility that systolic function changed during that window of time. Finally, the study size was fairly small with 71 subjects included in the final analysis.

Authors Conclusion

ED physicians can assess left ventricular systolic function using the EPSS, and EPSS is strongly correlated with calculated LVEF. An EPSS greater than 7 mm may be used to predict patients with severely reduced LVEF. ED physician visual estimation was less effective and less consistent than EPSS measurement for predicting systolic function.

Our Conclusion

We agree that EPSS is a feasible and useful tool for assessing systolic function at the bedside. This study establishes that a 7 mm EPSS cutoff is highly sensitive for detecting severe systolic dysfunction. The clinical utility of an EPSS cutoff of 8 mm for any systolic dysfunction is less clear. Employing EPSS measurement with the 7 mm cutoff in mind, in conjunction with visual estimation by an experienced ED sonographer, is likely to provide a more complete picture of a patient’s systolic function at the bedside prior to obtaining a formal echocardiogram.

The Bottom Line 

EPSS measured on bedside ultrasound the ED is an easily obtainable, quantitative predictor of systolic dysfunction. A cutoff of 7mm is sensitive in identifying systolic dysfunction.

Authors

This post was written by Jennie Xu, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD. 

References

McKaigney CJ, Krantz MJ, La Rocque CL, Hurst ND, Buchanan MS, Kendall JL. E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction. The American Journal of Emergency Medicine. 2014 Jun 1;32(6):493-7.

 

    1. Labovitz AJ, Noble VE, Bierig M, Goldstein SA, Jones R, Kort S, Porter TR, Spencer KT, Tayal VS, Wei K. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and American College of Emergency Physicians. Journal of the American Society of Echocardiography. 2010 Dec 1;23(12):1225-30.
    2.  Massie BM, Schiller NB, Ratshin RA, Parmley WW. Mitral-septal separation: new echocardiographic index of left ventricular function. The American journal of cardiology. 1977 Jun 1;39(7):1008-16.
    3. Lew W, Henning H, Schelbert H, Karliner JS. Assessment of mitral valve E point-septal separation as an index of left ventricular performance in patients with acute and previous myocardial infarction. The American journal of cardiology. 1978 May 1;41(5):836-45.
    4. Massie BM, Schiller NB, Ratshin RA, Parmley WW. Mitral-septal separation: new echocardiographic index of left ventricular function. The American journal of cardiology. 1977 Jun 1;39(7):1008-16.

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