What is the significance of E/E' ratio in determining a well-decongested patient with heart failure?

E/E' Ratio Measurement and Assessment of Decongestion in Heart Failure

An E/E' ratio ≤8 indicates normal left ventricular filling pressures and confirms adequate decongestion, while values >15 definitively indicate elevated filling pressures and persistent congestion. 1

Understanding the E/E' Ratio Components

The E/E' ratio combines two distinct Doppler measurements that together provide insight into left ventricular filling pressures:

• E wave: The early diastolic transmitral flow velocity measured by conventional pulsed-wave Doppler, reflecting the pressure gradient between the left atrium and left ventricle during early diastole 2
• e' velocity: The early diastolic mitral annular velocity measured by tissue Doppler imaging (TDI), primarily reflecting left ventricular relaxation with minimal influence from loading conditions 2

Proper Measurement Technique

• Measure e' at both septal and lateral mitral annulus positions and calculate the average for optimal assessment of global diastolic function 1, 2
• Septal e' values <8 cm/s, lateral e' <10 cm/s, or average e' <9 cm/s indicate delayed LV relaxation 1
• Proper sample volume positioning at the mitral annulus is critical for accurate e' measurement 2

Interpreting E/E' for Decongestion Status

Definitive Values

E/E' <8: Indicates normal LV filling pressures and confirms the patient is well-decongested 1, 2

E/E' >15 (or >14 for average values): Indicates high LV filling pressures and persistent congestion requiring continued diuresis 1, 2

The Gray Zone (E/E' 8-15)

• Values between 8-15 are indeterminate and require additional parameters to assess filling pressures 1
• In this range, incorporate:
  • Left atrial volume index >34 mL/m² suggests elevated pressures 1
  • Tricuspid regurgitation peak velocity >2.8 m/s indicates elevated pressures 1
  • Mitral inflow E/A ratio >2 suggests restrictive filling and volume overload 1

Clinical Application for Decongestion Assessment

At Hospital Discharge

• Target E/E' ≤15 before discharge to reduce readmission risk 3
• Patients with E/E' >15 after optimized medical therapy have significantly higher rates of heart failure readmissions and worse prognosis 3
• An E/E' threshold of approximately 13.8 has been validated as an inflection point for increased heart failure readmissions in acute HFpEF 4

Prognostic Significance

• Lower baseline E/E' in the acute phase independently predicts subsequent improvement of left ventricular ejection fraction in HFrEF patients 5
• E/E' >15 after optimized therapy is an independent predictor of cardiac events (risk ratio 6.1) in heart failure with preserved systolic function 3
• Septal E/E' at discharge has excellent accuracy (AUC 0.85) for predicting cardiac death 6

Important Caveats and Limitations

When E/E' May Be Unreliable

The E/E' ratio has limited accuracy in specific clinical scenarios 2:

• Heavy mitral annular calcification distorts tissue Doppler signals
• Mitral valve disease (stenosis or significant regurgitation) alters transmitral flow patterns
• Pericardial disease affects ventricular filling mechanics
• Regional wall motion abnormalities from coronary artery disease create heterogeneous annular velocities
• Atrial fibrillation causes beat-to-beat variability requiring averaging of multiple beats

Correlation Limitations

• The correlation between E/e' and invasively measured filling pressures is modest (r = 0.56), meaning approximately 30% of variance in filling pressures is explained by E/E' 2
• This underscores why E/E' should be integrated with other clinical and echocardiographic parameters rather than used in isolation

Practical Algorithm for Assessing Decongestion

1. Measure E/E' ratio (average of septal and lateral sites preferred) 1, 2

2. If E/E' ≤8: Patient is well-decongested; normal filling pressures confirmed 1

3. If E/E' >15: Patient remains congested; continue aggressive diuresis 1

4. If E/E' 8-15: Assess additional parameters:

   • Left atrial volume index 1
   • TR jet velocity 1
   • Mitral E/A ratio 1
   • If ≥2 of 3 parameters are abnormal: elevated filling pressures, inadequate decongestion 1
   • If ≤1 of 3 parameters abnormal: likely adequate decongestion 1

5. Correlate with clinical assessment: jugular venous pressure, peripheral edema, orthopnea, and natriuretic peptide levels 1

The goal of decongestion therapy is achieving E/E' ≤15 (ideally <8) combined with resolution of clinical congestion signs before hospital discharge to optimize outcomes and reduce readmissions. 4, 3