What test is used to measure ejection fraction (EF)?

Tests for Measuring Ejection Fraction (EF)

Transthoracic echocardiography (TTE) is the primary test used to measure ejection fraction due to its wide availability, non-invasive nature, and ability to provide real-time assessment of cardiac function. 1

Primary Imaging Modalities for EF Measurement

Transthoracic Echocardiography (TTE)

• First-line test for EF assessment as recommended by the American College of Cardiology/American Heart Association 1
• Uses the biplane method of disks (Simpson's method) requiring tracing of endocardial borders in two orthogonal views 2
• Calculation formula: EF = ([EDV - ESV]/EDV) × 100, where EDV is end-diastolic volume and ESV is end-systolic volume 2
• Advantages:
  • Widely available
  • Non-invasive
  • No radiation exposure
  • Real-time assessment
  • Cost-effective
• Limitations:
  • Operator-dependent
  • Image quality may be suboptimal in some patients
  • Intra- and inter-observer variability of 12.5% and 16.9% respectively, which can be reduced to 7.0% with contrast enhancement 3

Cardiac Magnetic Resonance Imaging (MRI)

• Gold standard for EF measurement 2
• Uses short-axis stack of images covering the entire ventricle with manual or semi-automated tracing of endocardial borders 2
• Advantages:
  • Highest accuracy and reproducibility
  • Excellent endocardial definition
  • Not limited by body habitus or acoustic windows
• Limitations:
  • Limited availability
  • Higher cost
  • Contraindicated in patients with certain implanted devices
  • Time-consuming

Alternative Imaging Modalities

Radionuclide Ventriculography (RNV)

• Class IIa recommendation when echocardiography is inadequate 1
• Can be used to assess LVEF and volumes 1
• Advantages:
  • Less operator-dependent than echocardiography
  • Good reproducibility
• Limitations:
  • Radiation exposure
  • Lower spatial resolution

Cardiac CT

• Uses similar principles to MRI but with radiation exposure 2
• Offers excellent spatial resolution
• Primarily used when other modalities are contraindicated or inadequate

Transesophageal Echocardiography (TEE)

• Not first-line for EF measurement but may be used in select patients 1
• Useful when transthoracic images are suboptimal
• More invasive than TTE, requiring sedation

Clinical Considerations

When to Repeat EF Measurement

• Routine repeat measurement of LV function in the absence of clinical status change is not recommended (Class III: No Benefit) 1
• Repeat measurement is useful in patients who have had:
  • Significant change in clinical status
  • Treatment that might affect cardiac function
  • Consideration for device therapy 1

Accuracy Considerations

• Different imaging modalities may yield slightly different EF values for the same patient
  • CMR typically measures higher EF values than TTE (median difference of 5%) 4
  • Only 64.4% of patients have their EF category confirmed by both TTE and CMR 4
• EF calculations are most accurate in ventricles with symmetric contraction
• Regional wall motion abnormalities reduce the accuracy of geometric assumptions

Special Situations

Contrast Enhancement for TTE

• Adding contrast significantly improves intra- and inter-observer variability for LV-EF measurement 3
• Beneficial in patients with both moderate-to-poor and good quality echocardiograms
• Reduces intra-observer variability from 12.5% to 7.0% and inter-observer variability from 16.9% to 7.0% 3

Right Ventricular EF

• Right ventricular fractional area change (RV FAC) can be calculated using: RV FAC = ([RV EDA – RV ESA]/RV EDA) × 100 2
• MRI is particularly valuable for right ventricular assessment

In conclusion, while multiple modalities can measure EF, transthoracic echocardiography remains the first-line test due to its wide availability and lack of radiation, with cardiac MRI serving as the gold standard when highest accuracy is required or when echocardiographic images are suboptimal.