Tests That Measure Ejection Fraction
Ejection fraction can be measured using several imaging modalities including echocardiography, cardiac MRI, nuclear imaging studies, CT scan, and cardiac catheterization. Each method has specific advantages and applications in clinical practice.
Primary Methods for Measuring Ejection Fraction
Echocardiography
Transthoracic Echocardiography (TTE): The most commonly used first-line test for measuring ejection fraction 1
- Uses the biplane method of disks (modified Simpson's rule) to calculate LVEF
- Formula: LVEF = ([EDV-ESV]/EDV) × 100, where EDV is end-diastolic volume and ESV is end-systolic volume 2
- Advantages: Non-invasive, widely available, no radiation exposure, relatively inexpensive
- Provides additional information about valvular function, wall thickness, and chamber size 1
Three-dimensional Echocardiography: Provides more accurate volumetric measurements
- Improves accuracy compared to 2D methods, especially for irregularly shaped ventricles
- Better correlation with gold standard methods like cardiac MRI 3
Transesophageal Echocardiography (TEE): Used when transthoracic windows are inadequate
- Can use multiple diameter method to determine EF without requiring volume calculations 4
Cardiac Magnetic Resonance Imaging (CMR)
- Considered the gold standard for ejection fraction measurement 1
- Provides highly accurate and reproducible measurements of ventricular volumes
- Particularly useful in patients with complex cardiac anatomy or poor echocardiographic windows
- Can be performed using both breath-hold and free-breathing techniques 1
- Allows assessment of myocardial viability, fibrosis, and tissue characterization
Nuclear Imaging
Myocardial Perfusion Imaging (SPECT):
- Measures LVEF through gated acquisition during perfusion studies 1
- Provides functional information alongside perfusion data
- Particularly useful in patients with suspected coronary artery disease
Radionuclide Ventriculography (MUGA scan):
- Provides reproducible quantification of ejection fraction
- Does not provide information about valvular function or wall thickness 1
Cardiac Computed Tomography (CT)
- Can measure ejection fraction as part of coronary CT angiography
- Provides ventricular volume assessment and regional wall motion analysis 1
- Higher radiation exposure compared to other non-invasive methods
Cardiac Catheterization with Ventriculography
- Invasive method that directly measures LVEF through contrast injection
- Left ventriculography can measure ejection fraction (range 5% to 90%) 1
- Usually performed when coronary angiography is indicated
- Provides additional hemodynamic data
Interpretation of Ejection Fraction Values
According to ACC/AHA guidelines 1, ejection fraction categories are:
- Hyperdynamic: >70%
- Normal: 50-70% (midpoint 60%)
- Mild dysfunction: 40-49% (midpoint 45%)
- Moderate dysfunction: 30-39% (midpoint 35%)
- Severe dysfunction: <30%
Clinical Considerations
Method selection should be based on:
- Clinical question (suspected valvular disease vs. coronary artery disease)
- Patient characteristics (body habitus, ability to lie flat)
- Local availability and expertise
- Need for additional cardiac information
Limitations to consider:
- Echocardiography may have suboptimal windows in obese patients or those with lung disease
- Different imaging modalities may yield slightly different EF values for the same patient
- Accuracy depends on image quality and operator experience
Common pitfalls:
- Failing to account for volume status when interpreting results
- Not considering the specific normal ranges for each modality
- Overlooking regional wall motion abnormalities when only focusing on global EF
For most patients, transthoracic echocardiography should be the initial test for measuring ejection fraction due to its wide availability, lack of radiation, and ability to assess multiple aspects of cardiac structure and function simultaneously 1.