What is the accuracy of Magnetic Resonance Imaging (MRI) ejection fraction?

Accuracy of MRI Ejection Fraction

MRI is the most accurate imaging technique for left ventricular ejection fraction (LVEF) quantification, with high correlation to invasive measurements when using multiple-slice imaging techniques.

Technical Accuracy of MRI LVEF Measurement

Correlation with Reference Standards

• Multiple-slice MRI technique shows excellent correlation with invasive ventriculography (r = 0.98), while single-slice techniques show only moderate correlation (r = 0.65) 1
• MRI slightly underestimates LVEF compared to radionuclide ventriculography, but with high correlation (r = 0.91) in patients with cardiomyopathy 2
• When properly performed with ECG-gated techniques and appropriate image planes oriented to left ventricular axes, MRI allows for accurate LVEF calculation 3

Methodological Considerations

• The accuracy of MRI LVEF depends significantly on the technique used:
  • Manual contouring and segmentation shows high accuracy
  • Semi-automatic techniques with manual adjustment of cardiac contours are time-saving and comparable to reference standards
  • Fully automated in-line tracking without adjustment may underestimate LVEF by overestimating end-systolic volume 4

Reproducibility

• MRI demonstrates excellent reproducibility for LVEF measurement:
  • High interobserver correlation (r = 0.91)
  • High intrapatient correlation (r = 0.98) 2
  • Lower interobserver variability compared to ventriculography (2.7 ± 7.8 vs 5.0 ± 6.9) 3

Clinical Utility and Prognostic Value

Prognostic Significance

• MRI-derived LVEF is a powerful predictor of major adverse cardiac events (MACE)
• Reduced LVEF (<40%) detected by MRI at any time during follow-up identifies patients at high risk of subsequent events
• Patients with reduced LVEF are 4.52 times more likely to experience MACE than those with mid-range LVEF (40-49%) 5

Clinical Applications

• MRI LVEF assessment is particularly valuable in:
  • Valvular heart disease
  • Congenital heart disease
  • Pulmonary hypertension
  • Heart failure 6
  • Post-myocardial infarction risk stratification 5

Comparison with Other Modalities

Advantages of MRI

• Provides comprehensive assessment of cardiac structure and function
• Does not rely on geometric assumptions for volume calculations
• Not limited by acoustic windows (unlike echocardiography)
• No ionizing radiation (unlike CT or nuclear techniques)
• Can simultaneously assess regional wall motion, tissue characterization, and viability

Limitations

• Requires specialized equipment and expertise
• More time-consuming than some other modalities
• May be contraindicated in patients with certain implants or severe claustrophobia
• Requires patient cooperation for breath-holding

Practical Considerations

Optimal Technique

• Multiple contiguous slice MRI technique is superior to single-slice methods
• ECG-gating is essential for accurate assessment
• Semi-automated techniques with manual adjustment provide the best balance of accuracy and efficiency
• Short-axis approach with multislice-multiphase technique is recommended for optimal results 2

Normal Values

• According to ACC/AHA guidelines, normal LVEF ranges from 50% to 70% (midpoint 60%)
• Hyperdynamic: >70%
• Mild dysfunction: 40-49% (midpoint 45%)
• Moderate dysfunction: 30-39% (midpoint 35%)
• Severe dysfunction: <30% 7, 6

In conclusion, when performed with appropriate technique, MRI provides highly accurate and reproducible measurements of LVEF that correlate strongly with invasive reference standards and offer significant prognostic value for clinical decision-making.