E/e′ Ratio: How to Calculate and Interpret It

Updated 5 November 2026 · Standard formula, shown below

The e/e′ ratio compares early mitral inflow velocity (E) with early mitral annular tissue velocity (e′) on a Doppler echocardiogram. It provides a noninvasive estimate used in assessing left ventricular filling pressure, but it is not a direct pressure measurement or a diagnosis by itself. You need the relevant echocardiogram measurements, recorded in the same units, and clinical interpretation by a qualified clinician.

What You’ll Need

A Doppler echocardiogram report or the ability to review the echocardiogram with an experienced cardiac sonographer or clinician.
The peak early transmitral inflow velocity, labeled E, and the early diastolic mitral annular tissue velocity, labeled e′ (sometimes written e-prime).
The e′ measurement from the septal annulus, lateral annulus, or both, clearly identified. Do not combine values from different locations without using the method specified by the interpreting clinician.
A calculator, if you want to divide the values yourself. Both measurements should use the same velocity units, commonly cm/s.

Step-by-Step

Find the E velocity. Look for the pulsed-wave Doppler measurement of early transmitral flow, often listed as “E,” “mitral E,” or “peak E velocity.” It is measured as blood flows from the left atrium into the left ventricle during early filling. Do not use the later A wave, which reflects atrial contraction.
Find the e′ velocity and its location. Tissue Doppler imaging measures the early diastolic motion of the mitral annulus. Reports may give a septal e′ and a lateral e′. These are not interchangeable: the septal value is often lower, so dividing E by it usually produces a higher ratio.
Confirm that the measurements are usable. Check that E and e′ are reported as peak velocities, not times or other Doppler values, and that the units match. If one value is absent, unclear, or marked technically limited, do not guess or substitute a different measurement.
Choose the calculation method specified for the report. If the clinician requests a septal ratio, divide E by septal e′. For a lateral ratio, divide E by lateral e′. Some assessments use the average of septal and lateral e′: first calculate the average e′, then divide E by that average. Follow the laboratory’s stated method; do not compare ratios calculated using different methods as if they were identical.
Divide E by the selected e′ value. For example, if E is 80 cm/s and septal e′ is 8 cm/s, then E/e′ = 80 ÷ 8 = 10. The units cancel, so the ratio is reported without units. Keep enough digits during calculation and round only for presentation.
Check the arithmetic and labels. Make sure the numerator is E and the denominator is e′. Confirm that the result agrees with the measurement location and method shown in the report. A ratio calculated from a lateral value cannot be relabeled as a septal ratio.
Interpret it in context. Use the ratio as one part of the echocardiographic assessment, alongside other measurements and the clinical picture. Do not use a single number to diagnose heart failure, estimate an exact pressure, or make treatment decisions.
Ask the interpreting clinician about a borderline or unexpected result. The clinician can check image quality, rhythm, valve findings, and other measurements, and explain what the result means for the particular examination.

Common Mistakes

Using the A wave instead of E: E is the early filling wave; A is associated with atrial contraction. Dividing A by e′ does not produce the standard E/e′ ratio.
Mixing septal and lateral measurements: These values can differ. State which e′ was used, or use the specified average method.
Mixing units: Convert both velocities to the same unit before dividing. For example, convert m/s to cm/s by multiplying by 100. Dividing values in unlike units gives a misleading result.
Assuming the ratio has units: When both velocities use the same units, those units cancel. The result is a dimensionless ratio.
Relying on a single cutoff: Reference ranges and interpretation depend on the measurement approach and the rest of the echocardiogram. A threshold should not be treated as a stand-alone diagnosis.
Calculating from poor-quality or mismatched readings: Measurements taken from different beats or under different conditions may not be comparable, particularly when the rhythm is irregular. Use the values selected and reported by the echocardiography team.

Tips

Write down the exact E, septal e′, and lateral e′ values, along with their units and labels, before calculating.
If both septal and lateral e′ values are supplied, ask which ratio the report uses. Do not assume an average unless the report or clinician says so.
Retain the unrounded result during the calculation. Report only the precision used by the laboratory or clinician; extra decimal places do not make the measurement more accurate.
Compare results over time only when the method and measurement site are comparable. Differences in equipment, technique, heart rhythm, or clinical conditions can affect measurements.
Read the full echocardiogram conclusion rather than interpreting an isolated ratio. E/e′ is one component of a broader assessment of diastolic function and filling pressure.

Troubleshooting

The report lists E but not e′: You cannot calculate E/e′ from E alone. Ask whether tissue Doppler measurements were obtained or whether the study needs review; do not estimate e′.
The report lists two e′ values but no ratio: Check whether it reports septal, lateral, or average E/e′ elsewhere. If not, ask the interpreting clinician which method applies before calculating.
The result seems unusually high or low: Recheck the numerator, denominator, units, and site label. Then have the clinician assess whether the measurements are reliable and how other findings affect interpretation.
There is an irregular rhythm or beat-to-beat variation: A single pair of values may not represent the examination reliably. The echocardiography team may need to use an appropriate set of beats and interpret the result with rhythm in mind.
The measurement is marked limited or is missing from an image: Do not fill in the value from another patient, an online table, or a different part of the report. Ask the clinician whether the study provides enough information or whether another assessment is needed.

Frequently Asked Questions

What does E/e′ measure?
It is the ratio of early transmitral blood-flow velocity (E) to early mitral annular tissue velocity (e′). It is used as an estimate related to left ventricular filling pressure, not as a direct pressure reading.

How do I calculate E/e′?
Divide E by the relevant e′ value. For instance, 80 cm/s divided by 8 cm/s equals 10. Use the septal, lateral, or averaged method specified for the examination.

Should I use septal or lateral e′?
Use the method stated in the report or requested by the clinician. Septal and lateral measurements can differ, so the resulting ratios should not be treated as equivalent.

Does E/e′ have units?
No, provided E and e′ are expressed in the same velocity units. The units cancel in the division.

Can E/e′ diagnose heart failure?
No. It is one echocardiographic measurement and must be interpreted with other findings and clinical information. A clinician should make the diagnosis.

Why might my E/e′ differ from an earlier result?
Measurement technique, the e′ site used, image quality, rhythm, and conditions at the time of the examination can all contribute. Ask the clinician to compare the methods and full reports.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.