How is ejection fraction calculated using 2D (Two-Dimensional) Echo methods?

Ejection Fraction Calculation Using 2D Echocardiography

Recommended Method: Biplane Method of Discs (Modified Simpson's Rule)

The biplane method of discs (modified Simpson's rule) using apical four-chamber and two-chamber views is the recommended 2D echocardiographic method for calculating ejection fraction, as it does not rely on geometric assumptions and is particularly reliable in abnormally shaped ventricles. 1, 2

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Step-by-Step Calculation Process

Step 1: Image Acquisition

• Obtain apical four-chamber view by positioning the transducer at the cardiac apex, ensuring the left ventricle is maximized without foreshortening 1, 2
• Obtain apical two-chamber view by rotating the transducer approximately 60-90 degrees from the four-chamber view 1, 2
• Optimize image quality to clearly visualize the endocardial border throughout the cardiac cycle 1
• Avoid foreshortening, which results in volume underestimation 1

Step 2: Identify Cardiac Phases

• End-diastole: Identify the frame with the largest left ventricular cavity size (typically at the R wave on ECG) 2
• End-systole: Identify the frame with the smallest left ventricular cavity size (typically just before mitral valve opening) 2

Step 3: Endocardial Border Tracing

• Trace the endocardial border at end-diastole in both apical four-chamber and two-chamber views 1, 2
• Trace the endocardial border at end-systole in the same views 1, 2
• Position electronic calipers on the interface between myocardial wall and cavity 1
• Include trabeculae and papillary muscles within the LV cavity for accurate volume calculation 1
• Trace from the mitral annulus to the apex and back to the opposite side of the annulus 1

Step 4: Volume Calculation

• The ultrasound machine automatically calculates volumes using the biplane method of discs by integrating segmental areas 2
• This method divides the left ventricle into multiple cylindrical discs of equal height 1
• End-diastolic volume (EDV) is calculated from the end-diastolic tracings 3
• End-systolic volume (ESV) is calculated from the end-systolic tracings 3

Step 5: Ejection Fraction Calculation

• Apply the formula: EF = [(EDV - ESV) / EDV] × 100 3, 2
• The ultrasound machine typically performs this calculation automatically after volume measurements 2

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Alternative 2D Methods (Less Preferred)

Single-Plane Method

• Uses only the apical four-chamber view when two-chamber view is inadequate 1
• Less accurate than biplane method, particularly in patients with regional wall motion abnormalities 4

Linear Measurement Methods (NOT Recommended)

• Teichholz and Quinones methods are no longer recommended as they rely on geometric assumptions (prolate ellipsoid shape) that do not apply in cardiac pathologies 1, 5
• M-mode derived measurements show poor agreement with reference standards 5

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Visual Estimation Method

For rapid bedside assessment when quantitative measurement is not feasible:

• Normal EF: >50% (vigorous contraction with near-obliteration of cavity) 2
• Moderately depressed EF: 30-50% (reduced but visible contraction) 2
• Severely depressed EF: <30% (minimal contraction with dilated cavity) 2
• Emergency physicians with limited training can accurately estimate EF visually, though quantitative measurement is preferred 2

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Important Technical Considerations

Image Quality Enhancement

• Harmonic imaging improves reproducibility of 2D LV volumes but uses lower frequencies that may reduce spatial resolution 2
• Contrast echocardiography provides volumes closer to cardiac MRI and improves endocardial border visualization 1, 6
• Contrast is particularly helpful in patients with suboptimal acoustic windows 1

Common Pitfalls to Avoid

• Foreshortening: Ensure true apical views by maximizing LV cavity area 1
• Oblique sections: Use 2D-guided measurements rather than M-mode to avoid oblique cuts 1
• Geometric assumptions: Never use linear dimension-based formulas (Teichholz, Quinones) as they are inaccurate in abnormal ventricles 1, 2
• Trabeculae exclusion: Include trabeculae within cavity to match MRI methodology and avoid underestimation 1

Special Circumstances

• Atrial fibrillation/tachycardia: Average measurements over multiple cardiac cycles 2
• Wall motion abnormalities: Biplane Simpson's method is superior to single measurements 4
• Poor acoustic windows: Consider contrast enhancement or alternative imaging modality 1, 6

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Measurement Variability and Limitations

• EF varies between imaging modalities and interpreters - a single measurement may not be adequate, particularly for borderline values (41-49%) 2
• 2D echo typically underestimates volumes compared to cardiac MRI 6, 5
• Load dependency: EF cannot distinguish between preload, afterload, and intrinsic contractility 2
• Reproducibility is better with contrast 2D echo than non-contrast 2D echo 6

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Normal Values and Classification

• Normal LVEF: 50-70% (midpoint 60%) 3, 2
• Mildly reduced: 40-49% 3, 2
• Moderately reduced: 30-39% 3, 2
• Severely reduced: <30% 3, 2
• Hyperdynamic: >70% 3, 2

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When to Consider 3D Echocardiography

3D echocardiography is recommended over 2D when available, as it provides more accurate and reproducible measurements with closer agreement to cardiac MRI 1. However, 3D requires good acoustic windows and has lower temporal resolution 1, 6.