Ejection Fraction in Echocardiography: Assessment of Left Ventricular Systolic Function
In echocardiography, ejection fraction is primarily used to assess left ventricular systolic function (option D). According to the American College of Cardiology/American Heart Association guidelines, ejection fraction is specifically defined as the proportion of blood ejected during left ventricular contraction of the heart 1.
Definition and Calculation of Ejection Fraction
Ejection fraction represents the percentage of blood volume that is pumped out of the left ventricle with each contraction. It is calculated using the formula:
- LVEF = ([EDV-ESV]/EDV) × 100
Where:
- LVEF = Left Ventricular Ejection Fraction
- EDV = End-Diastolic Volume (volume of blood in the left ventricle at the end of filling)
- ESV = End-Systolic Volume (volume of blood remaining after contraction) 1
Clinical Significance and Interpretation
The 2019 ACC/AHA/ASE guidelines classify left ventricular systolic function based on ejection fraction as follows:
- Normal: Left ventricular systolic function is normal (LVEF 50-70%)
- Hyperdynamic: Greater than normal proportion of blood ejected (LVEF >70%)
- Mildly reduced: Slightly reduced proportion of blood ejected (LVEF 40-49%)
- Moderately reduced: Moderately smaller proportion of blood ejected (LVEF 30-39%)
- Severely reduced: Considerably less blood ejected than normal (LVEF <30%) 1
Why Ejection Fraction Does Not Primarily Assess the Other Options
Let's examine why ejection fraction does not primarily assess the other options mentioned:
Valvular function (Option A): While valvular abnormalities can affect ejection fraction, specific parameters like velocity, pressure gradients, and valve area are used to directly assess valvular function. Ejection fraction measures the pumping efficiency of the left ventricle, not the function of heart valves.
Chamber size (Option B): Chamber size is assessed through direct measurements of ventricular dimensions, volumes, and wall thickness. While ejection fraction calculation uses chamber volumes, it primarily measures the contractile function rather than size itself.
Myocardial ischemia (Option C): While reduced ejection fraction may result from myocardial ischemia, it is not a direct measure of ischemia. Wall motion abnormalities, strain imaging, and stress testing are more specific for detecting ischemia.
Limitations of Ejection Fraction
Despite its widespread use, ejection fraction has several limitations:
- It is load-dependent and can be affected by preload and afterload conditions
- It may remain normal despite subclinical left ventricular dysfunction
- There can be significant variability between measurement methods (up to 10 points difference in approximately one-third of patients) 2
- It primarily reflects radial contraction and may miss early dysfunction in longitudinal fibers 3
Advanced Techniques Beyond Ejection Fraction
More sensitive techniques for assessing left ventricular function include:
- Global Longitudinal Strain (GLS): More sensitive for detecting early myocardial dysfunction than ejection fraction 3
- Tissue Doppler Imaging: Evaluates myocardial velocities
- Speckle Tracking Echocardiography: Allows assessment of myocardial deformation in multiple directions 4
However, despite these newer techniques, ejection fraction remains the cornerstone measurement for assessing left ventricular systolic function in clinical practice due to its established prognostic value and widespread familiarity among clinicians.