Ejection Fraction in Critical Care Echocardiography
Ejection Fraction (EF) is the percentage of blood ejected by the left ventricle (LV) during systole. It is the most commonly reported index of LV systolic function but should never be interpreted in isolation, especially in critically ill patients where preload, afterload, inotropes, vasopressors, and mechanical ventilation significantly influence EF.
Definition
Ejection Fraction (EF)
EF=EDV−ESV/(EDV) ×100
Where
- EDV = End-diastolic volume
- ESV = End-systolic volume
- Stroke Volume (SV) = EDV − ESV
Thus EF represents the fraction of LV end-diastolic volume expelled during systole.
Normal Values
EF (%) | Interpretation |
55–70% | Normal |
50–54% | Low-normal/borderline |
41–49% | Mildly reduced |
30–40% | Moderately reduced |
<30% | Severely reduced |
>70% | Hyperdynamic LV |
EF is NOT Contractility
This is one of the most important concepts in CCE.
EF depends upon
- Contractility
- Preload
- Afterload
- Heart rate
- Synchrony
- Valve lesions
Therefore Low EF ≠ poor myocardium and Normal EF ≠ normal myocardium
Determinants of EF
Determinant of Ejection Fraction (EF) | Effect on EF / Explanation |
Contractility | ↑ Contractility → ↓ End-systolic volume (ESV) → ↑ EF. Stronger myocardial contraction ejects a greater proportion of LV end-diastolic volume. Examples: Dobutamine, epinephrine, exercise. |
Preload | ↑ Preload → ↑ Stroke volume (Frank–Starling mechanism) → Slight ↑ EF (up to a limit). ↓ Preload → ↓ Stroke volume; EF may decrease or remain normal depending on contractility and afterload. |
Afterload | ↑ Afterload → ↓ LV ejection → ↑ ESV → ↓ EF. Common causes include hypertension, aortic stenosis, and vasoconstrictor/vasopressor therapy. |
Heart Rate | Extreme tachycardia shortens diastolic filling time, reducing preload and stroke volume. EF may become less reliable because of inadequate ventricular filling and beat-to-beat variability. |
Ventricular Dyssynchrony | Bundle branch block (especially LBBB), RV pacing, and electrical dyssynchrony reduce coordinated LV contraction, lowering stroke volume and EF. These patients may benefit from cardiac resynchronization therapy (CRT) if appropriate. |
Mitral Regurgitation (MR) | A portion of the LV stroke volume is ejected back into the left atrium, so EF may appear normal or even elevated despite reduced forward cardiac output. Therefore, EF overestimates true LV systolic function in significant MR. |
Methods of Measuring EF
Method | Accuracy | ICU Use |
Eyeballing (visual estimation) | Good in experts | Very common |
M-mode in PLAX | Poor | Rarely recommended |
Simpson biplane | Gold standard (2D) | Preferred when feasible |
EPSS | It is a surrogate marker only | Its quick |
M-mode EF
Measured in PLAX.
Cursor through
- LV cavity
- Mitral leaflet tips
- Papillary level
Measurements —LVIDd and LVIDs
Mathematical assumptions calculate EF.
Limitations
Not reliable when
- RWMA
- Dilated ventricles
- Septal abnormalities
- LV aneurysm
Hence rarely recommended today.
Simpson’s Biplane Method (Modified Simpson)
Gold Standard 2D Method
Recommended by:
- American Society of Echocardiography (ASE)
- European Association of Cardiovascular Imaging (EACVI)
Principle
- LV is divided into many small discs.
- Each disc volume calculated.
- Sum of discs=LV volume
- Volumes measured EDV and ESV
Views Required
- Apical 4-Chamber
- Apical 2-Chamber
Limitations
- Poor image quality
- Foreshortening
- Endocardial dropout
- Arrhythmias
- Tachycardia
EPSS (E-Point Septal Separation)
Definition
EPSS is the minimum distance between the anterior mitral valve leaflet (AML) and the interventricular septum during early diastole (E-wave).
It is measured in millimeters (mm).
A larger EPSS generally indicates reduced LV systolic function because the mitral valve leaflet no longer approaches the septum closely during rapid LV filling.
How to Measure EPSS
View-Parasternal Long-Axis (PLAX)
Mode-M-mode
Cursor Position
Place the M-mode cursor through:
- Tip of the anterior mitral leaflet
- Perpendicular to the leaflet motion
- Passing through the leaflet tips in the PLAX view
The M-mode tracing shows:
- D point (mitral valve opening)
- E point (maximum early diastolic opening)
- A point (atrial contraction)
- C point (mitral valve closure)
Measure the shortest distance between the E point and the interventricular septum.
|
EPSS |
Interpretation |
|
<5 mm |
Normal |
|
5–7 mm |
Borderline |
|
>7 mm |
Suggests reduced LV systolic function |
|
>10 mm |
Strongly suggests severe LV systolic dysfunction |
|
>15 mm |
Usually indicates markedly depressed EF |
Relationship Between EPSS and EF
There is an inverse relationship. Higher EPSS → Lower EF
EF (%) ≈ 75.5 − (2.5 × EPSS in mm)
|
EPSS |
Approximate EF |
|
2 mm |
~70% |
|
5 mm |
~63% |
|
10 mm |
~50% |
|
15 mm |
~38% |
|
20 mm |
~25% |
Important: This equation is only an approximation and should not replace Simpson’s biplane EF or 3D EF.
Limitations
|
Limitation |
Why it matters |
|
Not a direct measure of EF |
It is a surrogate marker only |
|
Dilated LV |
EPSS may increase because of chamber enlargement rather than isolated systolic dysfunction |
|
Aortic regurgitation |
Early closure of the mitral valve alters leaflet motion, making EPSS unreliable |
|
Mitral stenosis |
Restricted leaflet opening falsely increases EPSS |
|
Mitral valve prolapse |
Abnormal leaflet motion invalidates the measurement |
|
Prosthetic mitral valve |
Cannot be measured reliably |
|
Mitral annular calcification |
Restricts leaflet excursion |
|
Regional wall motion abnormalities |
Correlation with EF becomes less reliable |
|
Hypertrophic cardiomyopathy |
Small hyperdynamic LV may produce a very low EPSS despite abnormal physiology |
|
Tachycardia/atrial fibrillation |
Beat-to-beat variability reduces accuracy; average multiple beats |
|
Poor PLAX alignment |
Off-axis imaging leads to inaccurate measurements |
Pitfalls
- Measure the anterior mitral leaflet, not the posterior leaflet.
- Keep the M-mode cursor through the leaflet tips and perpendicular to leaflet motion.
- Do not rely on EPSS in patients with significant mitral valve disease or prosthetic mitral valves.
- Always interpret EPSS together with visual EF, LV size, MAPSE, S′, LVOT VTI, and the clinical picture.
Causes of Low EF
|
Cardiac Cause |
Non-cardiac / Secondary Cause |
|
Dilated cardiomyopathy |
Septic cardiomyopathy |
|
Myocardial infarction |
Severe acidosis |
|
Myocarditis |
Hypoxia |
|
Takotsubo syndrome |
Catecholamine depletion (late shock) |
|
End-stage hypertension |
Electrolyte disturbances |
|
Valvular heart disease |
Drug toxicity (e.g., anthracyclines) |
|
Infiltrative cardiomyopathy |
Severe malnutrition |
|
Tachycardia-induced cardiomyopathy |
Endocrine disorders (e.g., hypothyroidism) |
Causes of High EF
|
Cause |
Mechanism |
|
Septic shock (early) |
Low SVR with increased sympathetic drive |
|
Hypovolemia |
Small LV cavity empties almost completely |
|
Anemia |
High-output state |
|
Pregnancy |
Increased cardiac output |
|
Hyperthyroidism |
Increased contractility and heart rate |
|
Cirrhosis |
Hyperdynamic circulation |
|
Hypertrophic cardiomyopathy |
Small LV cavity with vigorous contraction |
|
Catecholamine infusion (e.g., dobutamine) |
Increased inotropy |
Limitations of EF in Critical Care
|
Limitation |
Explanation |
|
Load dependent |
Changes with preload and afterload |
|
Misses regional dysfunction |
Overall EF may remain preserved despite localized infarction |
|
Does not assess RV |
Reflects only LV systolic function |
|
Does not measure diastolic function |
A patient may have preserved EF but severe diastolic dysfunction (HFpEF) |
|
Preserved EF may mask low output |
Severe MR or AR can produce a normal/high EF with reduced effective forward flow |
|
Affected by tachyarrhythmias |
Beat-to-beat variability in atrial fibrillation or frequent ectopy reduces accuracy; average multiple beats |
|
Sensitive to image quality |
Poor acoustic windows and LV foreshortening underestimate volumes and distort EF |
|
Not a direct measure of contractility |
Influenced by loading conditions and ventricular synchrony |
Common Pitfalls
|
Pitfall |
Effect |
|
Foreshortened apical view |
Underestimates LV volumes; EF may be falsely high |
|
Poor endocardial border definition |
Inaccurate tracing and EF calculation |
|
Atrial fibrillation |
Average 5–10 cardiac cycles for a reliable estimate |
|
Frequent PVCs |
Measure only sinus beats after an appropriate recovery beat |
|
Significant MR/AR |
EF overestimates effective forward systolic performance |
|
Hyperdynamic septic state |
High EF does not exclude myocardial dysfunction |
|
RV failure |
LV EF may be normal despite severe shock from RV dysfunction |
|
Mechanical ventilation/PEEP |
Alters loading conditions and can change EF without intrinsic myocardial change |
EF Compared with Other Measures of LV Systolic Function
|
Parameter |
What it Measures |
Advantages |
Limitations |
|
EF |
Percentage of LV volume ejected |
Widely validated and familiar |
Load dependent; may miss subtle dysfunction |
|
Fractional Shortening (FS) |
Change in LV diameter |
Simple M-mode measurement |
Assumes normal LV geometry; less reliable with regional wall motion abnormalities |
|
MAPSE |
Longitudinal mitral annular excursion |
Quick, reproducible, useful in ICU |
Angle dependent; evaluates mainly longitudinal function |
|
Tissue Doppler S′ |
Longitudinal systolic annular velocity |
Sensitive to early dysfunction |
Angle dependent; affected by tethering |
|
Global Longitudinal Strain (GLS) |
Myocardial deformation |
Detects subclinical dysfunction earlier than EF |
Requires high-quality images and dedicated software; some load dependence |
|
LVOT VTI |
Stroke distance and surrogate of stroke volume |
Useful for cardiac output assessment and fluid responsiveness |
Does not directly measure LV contractility |
Current Guideline Recommendations
- Modified Simpson’s biplane method is the recommended 2D technique for routine quantification of LVEF by the American Society of Echocardiography (ASE) and the European Association of Cardiovascular Imaging (EACVI).
- Three-dimensional echocardiography is preferred over 2D when available because it avoids geometric assumptions and provides more accurate and reproducible LV volumes and EF.
- In critical care, visual estimation by experienced operators is acceptable for rapid bedside decision-making, but quantitative methods should be used whenever image quality and clinical circumstances permit.
High-Yield CCE Pearls
- Normal EF does not exclude shock.
- Low EF is not synonymous with poor contractility because EF is load dependent.
- Hyperdynamic EF is common in early sepsis, hypovolemia, and high-output states.
- Reduced EF in septic cardiomyopathy is often reversible over several days.
- Simpson’s biplane is the preferred 2D quantitative method; 3D EF is the most accurate echocardiographic technique.
- In ICU patients, serial EF trends are generally more informative than a single isolated EF measurement.
- Always integrate EF with clinical examination, hemodynamics, and the rest of the echocardiographic assessment rather than using it as the sole determinant of ventricular function.