What is the EA (early to late diastolic filling velocities) ratio in echocardiography (echo)?

E/A Ratio in Echocardiography

The E/A ratio is the ratio of early (E) to late (A) diastolic transmitral flow velocities measured by pulsed-wave Doppler echocardiography, serving as a fundamental parameter for assessing left ventricular diastolic function and filling patterns. 1, 2

Definition and Measurement

• E wave represents the peak velocity of early diastolic blood flow across the mitral valve, reflecting the pressure gradient between the left atrium and left ventricle during early diastole 2
• A wave represents the peak velocity of late diastolic flow resulting from atrial contraction 1
• The ratio is calculated by dividing the peak E velocity by the peak A velocity, measured using pulsed-wave Doppler with the sample volume positioned at the mitral valve leaflet tips 1, 3

Physiological Determinants

The E/A ratio is influenced by multiple factors:

• Left ventricular relaxation (lusitropy) - impaired relaxation reduces early filling and the E wave 2, 4
• Left atrial pressure at mitral valve opening - elevated pressure increases the E wave 2, 4
• Left ventricular compliance (chamber stiffness) - reduced compliance affects filling patterns 4
• Age - normal E/A ratio decreases with age; young individuals (<40 years) may have E/A ratios >2 as a normal finding 1

Clinical Interpretation for Diastolic Dysfunction Grading

Grade I Diastolic Dysfunction (Impaired Relaxation)

• E/A ratio ≤0.8 with peak E velocity ≤50 cm/sec indicates normal or low mean left atrial pressure 1, 2
• This pattern reflects impaired left ventricular relaxation with normal filling pressures 1

Grade III Diastolic Dysfunction (Restrictive Pattern)

• E/A ratio ≥2 indicates elevated left atrial pressure and advanced diastolic dysfunction 1, 2
• Deceleration time is typically <160 msec, though it can exceed this when E velocity is >120 cm/sec 1
• In young individuals (<40 years), E/A >2 may be normal and requires confirmation with other parameters like annular e' velocity 1

Intermediate Patterns (Grade II)

• E/A ratio between 0.8-2.0 or E/A ≤0.8 with E velocity >50 cm/sec requires additional parameters for accurate assessment 1, 2
• Use E/e' ratio, tricuspid regurgitation peak velocity, and left atrial volume index to determine filling pressures 1

Special Clinical Scenarios

Atrial Fibrillation

• Only the E wave is present (no organized atrial contraction), so E/A ratio cannot be calculated 1
• Alternative parameters include E wave acceleration rate (≥1,900 cm/sec²), IVRT (≤65 msec), and E/e' ratio (septal ≥11) 1

Recent Cardioversion

• Use deceleration time instead of E/A ratio due to left atrial stunning causing markedly reduced A velocity despite normal filling pressures 1
• The artificially elevated E/A ratio (≥2) does not reflect true diastolic dysfunction in this context 1

First-Degree AV Block and Pacing

• PR interval >280 msec causes fusion of E and A waves, making E/A ratio unreliable 1
• Fusion occurs when atrial contraction happens before early diastolic flow has decreased to ≤20 cm/sec 1
• This creates an artificially reduced E/A ratio that mimics impaired relaxation pattern 1

Mitral Regurgitation

• Moderate-to-severe mitral regurgitation elevates peak E velocity and can create pseudonormal or restrictive patterns independent of true diastolic dysfunction 1
• In patients with depressed ejection fraction and mitral regurgitation, E/A ratio combined with E/e' >14 predicts hospitalizations and mortality 1

Sinus Tachycardia

• When E and A velocities are fused, use compensatory periods after premature beats to allow separation for accurate measurement 1
• Mitral inflow pattern with predominant early filling in patients with ejection fraction <50% suggests elevated filling pressures 1

Integration with Other Parameters

The E/A ratio should never be interpreted in isolation - it must be combined with:

• E/e' ratio - average E/e' >14 indicates elevated filling pressures with high specificity 1, 2
• Tricuspid regurgitation peak velocity - >2.8 m/sec supports elevated filling pressures 1
• Left atrial volume index - >34 mL/m² suggests chronically elevated pressures 1
• Deceleration time - <160 msec with E/A ≥2 confirms restrictive physiology 1

Common Pitfalls

• Do not rely on E/A ratio alone when values fall between 0.8-2.0, as this represents a "gray zone" requiring additional assessment 1
• Age-adjust your interpretation - E/A ratio normally decreases with age, and young patients may have E/A >2 as a normal variant 1
• Recognize pseudonormalization - E/A ratio 0.8-2.0 may represent either normal function or pseudonormal pattern (grade II dysfunction) requiring tissue Doppler to differentiate 1
• Avoid measurement during arrhythmias - atrial fibrillation eliminates the A wave, and frequent ectopy prevents accurate assessment 1