How To Calculate Ejection Fraction From Echocardiography

Calculate left ventricular ejection fraction (LVEF) using direct end-diastolic and end-systolic volumes or Teichholz-based diameter estimates.

How to Calculate Ejection Fraction from Echocardiography: Complete Clinical Guide

Ejection fraction (EF) is one of the most frequently used quantitative measurements in cardiology. In everyday practice, clinicians rely on EF to assess left ventricular systolic function, classify heart failure phenotypes, estimate prognosis, and guide medication and device therapy. Although EF is conceptually simple, the quality of the number depends heavily on image acquisition, measurement technique, and interpretation context. This guide explains exactly how to calculate EF from echocardiography, what methods are most reliable, and how to interpret the result safely.

What EF Measures and Why It Matters

Left ventricular ejection fraction is the proportion of blood ejected by the left ventricle during systole relative to the blood present at end diastole. In practical terms, EF is a percentage that reflects pumping efficiency. An EF of 60% means that about 60% of the blood in the ventricle at end diastole is expelled with each beat, while 40% remains in the ventricle at end systole.

EF is central for diagnosing and phenotyping heart failure:

• HFrEF: EF less than 40%
• HFmrEF: EF 41% to 49%
• HFpEF: EF 50% or higher

These categories influence therapeutic decisions, follow-up strategy, and risk counseling. EF is also used in valvular heart disease, cardiomyopathy surveillance, cardio-oncology, and post myocardial infarction care.

Core Formula for Ejection Fraction

The EF formula is straightforward:

EF (%) = [(EDV – ESV) / EDV] × 100
EDV = End-diastolic volume, ESV = End-systolic volume

If EDV is 120 mL and ESV is 50 mL, stroke volume is 70 mL and EF is 58.3%. The formula itself is not the difficult part. The challenge is obtaining accurate EDV and ESV from echo images.

Main Echocardiographic Methods Used to Calculate EF

1) Simpson Biplane Method of Disks (Preferred in 2D Echo)

The Simpson biplane method estimates LV volume by tracing endocardial borders in two orthogonal apical views, usually apical 4-chamber and apical 2-chamber. The ventricle is mathematically divided into stacked disks. Summing the disk volumes provides EDV and ESV, from which EF is calculated.

This approach is preferred over linear methods because it accommodates non-uniform ventricular geometry better, especially after infarction or remodeling.

2) Teichholz (M-Mode or 2D Linear Dimensions)

Teichholz uses LV diameters to estimate volumes with geometric assumptions:

• EDV ≈ 7 / (2.4 + LVEDD) × LVEDD³
• ESV ≈ 7 / (2.4 + LVESD) × LVESD³
• EF = (EDV – ESV) / EDV × 100

It is quick, but accuracy drops in ventricles with regional wall motion abnormalities or asymmetric dilation. It can still be useful in limited studies or as a rough estimate.

3) 3D Echocardiography

Three-dimensional echo can measure LV volumes without many of the geometric assumptions used in 2D methods. In experienced labs with good image quality, 3D EF often shows better reproducibility and closer agreement with cardiac magnetic resonance (CMR), commonly considered the noninvasive reference standard for LV volumes.

Method	Typical Geometric Assumption Burden	Typical Interobserver Variability	Clinical Practicality
2D Simpson Biplane	Moderate	About 8% to 12% for EF in routine practice	High, widely available
Teichholz Linear	High	About 10% to 15% when geometry is abnormal	Very high, rapid but less robust
3D Echo Volumetric	Low to moderate	About 5% to 8% in good image windows	Increasing availability
CMR (reference comparison)	Low	About 3% to 5%	Excellent accuracy, lower accessibility

Step-by-Step: Calculating EF Correctly in Daily Practice

1. Acquire high-quality apical images. Foreshortening can significantly underestimate EDV and distort EF. Ensure the true apex is captured.
2. Select the right cardiac phases. End diastole is typically the frame with largest LV cavity. End systole is the smallest LV cavity.
3. Trace endocardial borders carefully. Include trabeculations and papillary muscles consistently according to lab protocol.
4. Use biplane tracing when possible. Avoid single-plane shortcuts in ventricles with regional dysfunction.
5. Calculate EDV, ESV, and EF. Apply the formula exactly and verify EDV is greater than ESV.
6. Validate plausibility. If EF is inconsistent with clinical picture, recheck tracing and image quality, and consider contrast echo or CMR.

Normal and Abnormal EF Ranges

Guideline sources vary slightly by sex and method, but broadly accepted adult interpretation is:

• Normal: about 52% to 72% in men, 54% to 74% in women (method dependent)
• Mildly reduced: around 41% to 51%
• Moderately reduced: around 30% to 40%
• Severely reduced: less than 30%

Remember that a normal EF does not exclude heart failure. In HFpEF, EF may be preserved while filling pressures, diastolic function, atrial pressures, and strain are abnormal.

Outcome-Relevant EF Bands in Clinical Literature

EF Band	Typical Clinical Interpretation	General Risk Pattern Seen in HF Cohorts
< 30%	Severe systolic dysfunction	Highest hospitalization and cardiovascular mortality burden
30% to 39%	Moderate to severe reduction	Substantially elevated adverse event rates versus preserved EF groups
40% to 49%	Mild reduction / HFmrEF range	Intermediate risk profile, often between HFrEF and HFpEF
≥ 50%	Preserved EF range	Lower systolic failure risk but still meaningful morbidity in HFpEF phenotypes

Worked Examples

Example 1: Simpson Volumes

Suppose EDV is 140 mL and ESV is 70 mL. Stroke volume is 70 mL. EF is:

EF = (140 – 70) / 140 × 100 = 50%

This lands at the lower edge of preserved or mildly reduced range depending on local lab thresholds.

Example 2: Teichholz Diameter Conversion

If LVEDD is 5.6 cm and LVESD is 4.2 cm:

• EDV ≈ 7 / (2.4 + 5.6) × 5.6³ = about 153.7 mL
• ESV ≈ 7 / (2.4 + 4.2) × 4.2³ = about 78.6 mL
• EF ≈ (153.7 – 78.6) / 153.7 × 100 = about 48.9%

This is a reasonable quick estimate but should be interpreted with caution if there are wall motion abnormalities.

Common Errors That Distort EF

• Apical foreshortening: underestimates EDV and can artifactually alter EF.
• Poor border definition: introduces major tracing variability.
• Beat selection errors: especially problematic in atrial fibrillation and ectopy.
• Inconsistent papillary inclusion: can shift measured cavity volume.
• Using linear methods in distorted ventricles: can misclassify systolic function.

Quality Improvement Tips for Echo Labs

1. Use contrast enhancement when endocardial borders are suboptimal.
2. Standardize tracing conventions across sonographers and readers.
3. Track interobserver variability and run periodic calibration sessions.
4. Prefer serial comparisons in the same lab and method for trend reliability.
5. In borderline decisions, corroborate with strain imaging or CMR.

EF Interpretation in Broader Clinical Context

EF is critical but not sufficient as a standalone marker. A complete echo interpretation should include LV size, wall thickness, regional wall motion, right ventricular function, valvular lesions, diastolic indices, left atrial volume, and pulmonary pressure estimates. Patients with severe mitral regurgitation can have deceptively preserved EF despite impaired forward output. Conversely, bradycardic patients may have adequate EF but low cardiac output due to low heart rate.

Cardio-oncology adds another layer: a patient may have a statistically significant decline in EF from baseline even while remaining in a so-called normal range. In these scenarios, longitudinal strain and serial trend interpretation become essential.

When to Repeat EF and When to Escalate Imaging

• Repeat EF after major therapy changes in HFrEF.
• Reassess after myocardial infarction, especially if revascularization status changes.
• Repeat when symptoms worsen despite stable prior EF.
• Escalate to contrast echo or CMR when image quality is limited or values are discordant with clinical findings.

Authoritative Resources

For patient-centered and professional reference material, review:

• National Heart, Lung, and Blood Institute (.gov): Heart failure diagnosis and imaging context
• MedlinePlus (.gov): Echocardiography overview
• University of Rochester Medical Center (.edu): Ejection fraction clinical explanation

Bottom Line

To calculate ejection fraction from echocardiography, use EF = (EDV – ESV) / EDV × 100. In modern practice, Simpson biplane is generally preferred for 2D studies, while Teichholz is a backup estimate when only linear dimensions are available. The final number should always be interpreted with image quality, rhythm, loading conditions, and the broader clinical picture in mind. Precision in acquisition and consistency in method are what make EF actionable and reliable over time.