Understanding the role of tissue Doppler e′

Understanding the role of tissue Doppler e′
in the 2025 ASE Diastolic Function Guidelines
For years, one number has dominated discussions of diastolic function: The E/e′ ratio.

It appears on nearly every echocardiography report (or at least it should) and is frequently used as a surrogate for estimating left ventricular filling pressures. But in the process, one of the most important measurements in diastology often gets overlooked—the e′ velocity itself. The 2025 American Society of Echocardiography (ASE) Guidelines for the Evaluation of Left Ventricular Diastolic Function remind us of an important principle:


Before you interpret the E/e′ ratio, you must first understand the e′ velocity.

What is e′?
The e′ (e-prime) velocity is measured using tissue Doppler imaging (TDI) of the mitral annulus. Unlike transmitral inflow velocities, which measure blood movement, tissue Doppler measures the motion of the myocardium (or annulus) itself.
Specifically, e′ represents:

• Active left ventricular relaxation
• Early diastolic myocardial lengthening
• The ability of the ventricle to create suction during early filling

Simply put:
e′ tells us how well the ventricle relaxes.

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Why Relaxation Matters
Normal diastolic filling depends on efficient myocardial relaxation.
When the ventricle relaxes normally:

• LV pressure rapidly falls
• The ventricle creates suction
• Blood flows easily from the left atrium
• Filling occurs at relatively low atrial pressures

As relaxation becomes impaired:

• Ventricular pressure falls more slowly
• Suction decreases
• Filling becomes less efficient
• The left atrium must generate higher pressure to maintain cardiac output

One of the earliest echocardiographic signs of impaired relaxation is a reduced e′ velocity.
This often occurs before filling pressures become elevated.
That makes e′ one of the earliest indicators of diastolic dysfunction.

Measuring e′
The ASE recommends obtaining tissue Doppler velocities from the:

• Septal mitral annulus
• Lateral mitral annulus

Because myocardial relaxation is not uniform throughout the ventricle, these velocities differ slightly.
Typical normal values are approximately:
Septal e′

• ≥7 cm/sec

Lateral e′

• ≥10 cm/sec

Values below these thresholds suggest impaired myocardial relaxation.
Notice something important:
These measurements tell us about relaxation—not filling pressure.

A Low e′ Does NOT Automatically Mean Elevated Filling Pressures
This is one of the biggest misconceptions in echocardiography.
A patient may have:

• Reduced septal e′
• Reduced lateral e′
• Grade I diastolic dysfunction

…and still have normal left atrial pressure.
Why?
Because impaired relaxation occurs first.
Only later, when the ventricle becomes stiff enough that filling requires increased atrial pressure, do filling pressures begin to rise.
That distinction is exactly why the 2025 ASE algorithm evaluates multiple variables instead of relying on one measurement.

Now Add the E Wave
Once we understand relaxation, we can better appreciate the purpose of the E/e′ ratio.
The ratio combines two different physiologic processes.
E wave

• Represents transmitral blood flow
• Influenced by left atrial pressure

e′

• Represents myocardial relaxation

By dividing E by e′, we ask an important physiologic question:
"How much filling velocity is occurring relative to the ventricle's ability to relax?"
If relaxation is poor but filling remains modest, the ratio stays relatively low.
If relaxation is poor and filling velocity is high because left atrial pressure has increased, the ratio rises.
This is why the E/e′ ratio is considered an estimate of left ventricular filling pressure, rather than simply a measure of diastolic dysfunction.

The Role of E/e′ in the 2025 ASE Guidelines
One of the major themes of the 2025 ASE Diastolic Function Guidelines is that E/e′ is no longer viewed as a standalone diagnostic measurement.
Instead, it serves as one component of a comprehensive assessment that also includes:

• e′ velocity
• TR velocity or estimated pulmonary artery systolic pressure
• Left atrial volume index (LAVI)
• Left atrial reservoir strain (LARS)
• Pulmonary vein Doppler (when appropriate)
• Clinical presentation

The emphasis has shifted from asking:
"Is the E/e′ elevated?"
to asking:
"Does the entire physiologic picture support elevated filling pressures?"
That is a much more powerful—and accurate—approach.

Think Physiology, Not Ratios
A useful way to approach diastology is to separate the questions.
Question 1:Is the ventricle relaxing normally?
Answer that with e′.
Question 2:If relaxation is impaired, have filling pressures become elevated?
Answer that with E/e′, interpreted alongside the rest of the ASE algorithm.
Understanding this sequence makes the entire diastolic evaluation much easier to understand.

Clinical Pearl
Many sonographers jump immediately to the E/e′ ratio, but experienced echocardiographers often begin somewhere else.
They first examine the e′ velocity. Because before you can determine whether filling pressures are elevated, you first need to know how well the ventricle relaxes.
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The 2025 ASE Diastolic Function Guidelines reinforce that philosophy by placing myocardial relaxation at the center of diastolic assessment and using the E/e′ ratio as one piece of a much larger physiologic puzzle—not the entire answer.
When you understand e′ first, the E/e′ ratio becomes far more meaningful. And ultimately, that leads to better interpretation, more accurate grading of diastolic dysfunction, and better patient care.