What is the best method for quantifying ejection fraction (EF) and how is it used to guide management of heart failure?

Ejection Fraction Quantification and Its Role in Heart Failure Management

Transthoracic echocardiography is the preferred method for quantifying ejection fraction (EF) due to its non-invasiveness, reliability, wide availability, and ability to provide comprehensive information about cardiac structure and function beyond just EF measurement. 1

Best Methods for Quantifying Ejection Fraction

Primary Methods (In Order of Preference)

1. Transthoracic Echocardiography (TTE)

   • Advantages:
     • Non-invasive and safe
     • Provides comprehensive information about:
       • Ventricular function
       • Chamber size and shape
       • Wall thickness
       • Valvular function
     • Widely available and relatively inexpensive
     • Can differentiate systolic from diastolic dysfunction
   • Techniques:
     • Simpson's biplane method (most accurate 2D method)
     • Visual estimation ("eyeballing") by experienced cardiologists correlates well with quantitative methods 2

2. Radionuclide Ventriculography

   • Advantages:
     • Provides reproducible quantification of EF
     • Can assess both left and right ventricular EF
   • Limitations:
     • Does not provide information about valvular function or wall thickness
     • Involves radiation exposure

3. Cardiac Magnetic Resonance Imaging (CMR)

   • Advantages:
     • Gold standard for accuracy
     • Excellent for assessing myocardial infiltration or scar
     • 3D approach for non-symmetric ventricles
   • When to use:
     • When echocardiography is inadequate
     • When assessing myocardial infiltrative processes or scar burden
   • Limitations:
     • Limited availability
     • Higher cost
     • Contraindicated in some patients (implants, claustrophobia)

Clinical Significance of EF in Heart Failure Management

Classification Based on EF

EF measurement is critical for categorizing heart failure:

• HFrEF (Heart Failure with reduced EF): EF < 40%
• HFmrEF (Heart Failure with mildly reduced EF): EF 40-49%
• HFpEF (Heart Failure with preserved EF): EF ≥ 50%

Treatment Decisions Based on EF

1. Medication Selection

   • HFrEF (EF < 40%):
     • ACE inhibitors/ARBs
     • Beta-blockers
     • Mineralocorticoid receptor antagonists (spironolactone)
     • SGLT2 inhibitors
     • Ivabradine (for patients with EF ≤ 35% and heart rate ≥ 70 bpm) 3

2. Device Therapy Decisions

   • Implantable cardioverter-defibrillators (ICDs) for patients with EF ≤ 35%
   • Cardiac resynchronization therapy (CRT) consideration for patients with EF ≤ 35% and wide QRS

3. Monitoring Disease Progression

   • Serial EF measurements help assess response to therapy
   • Improvement in EF may guide medication adjustments
   • Note: Routine repeat measurement without clinical status change is not recommended 1

Important Considerations and Pitfalls

1. Intermethod Variability

   • Different methods for measuring EF are not interchangeable 4
   • Variations between techniques:
     • EF measurements by echocardiography and left ventriculography can differ by >10 points in approximately one-third of patients 5
     • Wide limits of agreement between methods, particularly with echocardiography

2. Technical Limitations

   • Image quality affects accuracy of echocardiographic EF measurements
   • Not all patients have adequate acoustic windows for reliable measurements
   • Operator experience significantly impacts accuracy

3. Integrated Assessment

   • EF should not be the sole parameter for assessing heart function
   • Consider other parameters:
     • Left atrial volume index (LAVI)
     • E/e' ratio (for diastolic function)
     • Global longitudinal strain (more sensitive for early dysfunction)
     • Natriuretic peptide levels

4. Documentation Challenges

   • EF may be reported as a specific number, range, or qualitative description
   • Standardized reporting improves clinical decision-making 6

Algorithm for EF Assessment in Heart Failure

1. Initial Diagnosis

   • Perform transthoracic echocardiography for all patients with suspected heart failure
   • Document EF using Simpson's biplane method when possible

2. If TTE is Inadequate

   • Consider radionuclide ventriculography or CMR

3. Follow-up Assessment

   • Repeat EF measurement when:
     • Clinical status changes significantly
     • After initiating new heart failure therapy
     • When considering device therapy
     • Not routinely without clinical changes

4. Special Situations

   • Consider cardiac catheterization when:
     • Significant coronary artery disease is suspected
     • Valvular heart disease would affect treatment
     • Surgical intervention is being considered

By following this evidence-based approach to EF quantification, clinicians can accurately diagnose heart failure, guide appropriate therapy, and monitor disease progression to improve patient outcomes.