What is Ejection Fraction?
Ejection fraction (EF) is the percentage of blood ejected from a ventricle during contraction of the heart, calculated as the difference between end-diastolic volume (EDV) and end-systolic volume (ESV) divided by end-diastolic volume, multiplied by 100. 1
Definition and Calculation
- Left ventricular ejection fraction (LVEF) is defined as the proportion of blood ejected during left ventricular contraction of the heart 1
- The formula for calculating ejection fraction is: LVEF = ([EDV-ESV]/EDV) × 100 1
- EDV is the volume of blood in the ventricle at the end of filling (diastole) 1
- ESV is the volume of blood remaining in the ventricle after contraction (systole) 1
Clinical Significance and Interpretation
- LVEF is a key measure of cardiac systolic function and serves as a critical parameter for diagnosis, prognosis, and treatment decisions 1
- Normal LVEF typically ranges from 50-70% 2
- LVEF classifications according to the American College of Cardiology/American Heart Association 1:
- Normal: Left ventricular systolic function is normal
- Hyperdynamic: Greater than normal proportion of blood is ejected during systole
- Mildly reduced: The proportion of blood ejected is slightly reduced compared to normal
- Moderately reduced: The proportion of blood ejected is moderately smaller than normal
- Severely reduced: The proportion of blood ejected is considerably less than normal
Clinical Applications
- LVEF is used to categorize heart failure types 1:
- Heart failure with preserved ejection fraction (HFpEF): LVEF ≥50%
- Heart failure with mildly reduced ejection fraction (HFmrEF): LVEF 40-49%
- Heart failure with reduced ejection fraction (HFrEF): LVEF <40%
- LVEF is a powerful predictor of cardiovascular outcomes across a broad spectrum of heart failure patients 3
- Mortality risk increases by 39% for every 10% reduction in ejection fraction below 45% 3
Measurement Methods
- LVEF can be estimated visually by echocardiography or calculated using volumetric measurements 1
- Other imaging modalities used to measure EF include cardiac MRI, nuclear imaging, and cardiac CT 4
- Right ventricular ejection fraction (RVEF) can also be measured and has similar clinical significance for right heart function 1
Limitations
- Despite its widespread use, EF has several limitations 5, 4:
- It reflects relative volume changes rather than the mechanism of pumping action 5
- It has limited sensitivity for detecting early or subclinical left ventricular dysfunction 4
- It may not accurately represent cardiac function in certain conditions like valvular heart disease 4
- It can vary between different imaging modalities and interpreters 1
Clinical Context
- EF is a cornerstone measurement in modern cardiology that pervades guidelines and practice 4
- It's particularly important in elderly patients, especially women with systolic hypertension who may have heart failure despite normal EF 6
- Changes in EF over time can provide valuable prognostic information in heart failure patients 7
EF remains a fundamental parameter in cardiovascular medicine despite its limitations, serving as an essential tool for risk stratification and therapeutic decision-making in heart failure and other cardiac conditions.