Right Ventricle: Size and Function Norms According to ASE 2025
Clinical Significance of ASE 2025 Update
The ASE 2025 guidelines for assessing the right chambers mark a practical shift: the right ventricle should be described quantitatively but interpreted comprehensively. Due to the complex shape of the RV, linear dimensions remain useful for screening dilation but do not replace the assessment of area, volume, longitudinal function, 3D ejection fraction, and hemodynamics.
For the ultrasound diagnostician, the main takeaway is that the standard echocardiography protocol should include an RV-focused apical 4-chamber view, measurements of the RV at end-diastole, at least one parameter of longitudinal systolic function, and pressure calculation if adequate tricuspid regurgitation is present.
How to Obtain RV-focused A4C
The classic apical 4-chamber view often underestimates the true size of the RV because the plane is oriented towards the left ventricle. In RV-focused A4C, the probe is shifted and rotated to maximize the view of the RV free wall, RV apex, and tricuspid annulus. Measurements are taken at end-diastole, usually in the frame before tricuspid valve closure or at the point of maximum ventricular size.
It is important not to 'cut off' the RV: if the apex is formed by the left ventricle, the longitudinal size of the RV will be underestimated. If the lateral wall exits the sector, the basal diameter may be overestimated or non-reproducible.
Right Ventricle Sizes: Working References
ASE 2025 maintains the need to specify from which position the sizes are obtained. For linear RV assessment in RV-focused A4C, the basal diameter, mid-diameter, and longitudinal size are used. RV dilation is particularly significant if it is associated with right atrial enlargement, IVC dilation, increased tricuspid regurgitation velocity, or reduced function.
| Parameter | How to Measure | ASE Reference / Threshold |
|---|---|---|
| RV Basal Diameter | RV-focused A4C, end-diastole, maximum transverse size in the basal third | up to 41 mm |
| RV Mid-Diameter | RV-focused A4C, transverse size in the mid-third | up to 35 mm |
| RV Longitudinal Size | From the plane of the tricuspid annulus to the RV apex | up to 83 mm |
| RV Free Wall Thickness | Subcostal, end-diastole, excluding trabeculae | up to 5 mm |
| TAPSE | M-mode through the lateral tricuspid annulus | ≥17 mm |
| S′ of the Lateral Tricuspid Annulus | Tissue Doppler, lateral tricuspid annulus | ≥9.5 cm/s |
| RV FAC | 100 × (EDA − ESA) / EDA, RV-focused A4C | ≥35% |
| 3D-RVEF | 3D RV volumes excluding the right atrium and trabeculae by accepted methodology | ≥45% |
| RV Free-Wall Strain | Speckle-tracking of the RV free wall | more negative than −20% |
Systolic Function: Not a Single Indicator
TAPSE and S′ primarily reflect longitudinal shortening of the RV basal segment. They are simple, reproducible, and mandatory in most routine studies but depend on angle, heart translation, postoperative state, and load. Therefore, normal TAPSE does not exclude RV dysfunction if FAC, 3D-RVEF, or strain are reduced.
FAC assesses the change in RV area and better reflects global 2D systolic function than isolated annular motion. When calculating FAC, the contour is traced along the endocardium at end-diastole and end-systole, including the apex and excluding trabeculae as much as image quality allows.
3D Echocardiography of the Right Ventricle
ASE 2025 emphasizes that 3D echocardiography is preferable for RV volumes and ejection fraction when technical capability and sufficient data quality are available. This is especially important in congenital defects, pulmonary hypertension, significant tricuspid regurgitation, cardiomyopathies, and therapy monitoring.
The key limitation is the quality of the complete volume set. If the RV free wall or outflow tract falls out of the volume, the 3D-RVEF calculation is unreliable. It is advisable to note in the report if the 3D assessment was not performed due to technical reasons.
RV Strain: When It Is Especially Useful
Longitudinal strain of the RV free wall detects subclinical dysfunction earlier than TAPSE or FAC. In a practical protocol, the parameter is especially useful in pulmonary hypertension, oncocardiology follow-up, cardiomyopathies, and borderline standard indicator values. The same software package should be used for dynamic monitoring, as strain values depend on the tracking algorithm.
Right Atrium and IVC
The RV is always interpreted together with the right atrium. Enlargement of the right atrium supports the diagnosis of chronic pressure or volume overload and increases the likelihood of clinically significant right chamber pathology. The inferior vena cava is used to assess right atrial pressure: a diameter up to 21 mm with more than 50% collapse corresponds to low pressure; a diameter greater than 21 mm with less than 50% collapse indicates high pressure; intermediate variants require clinical and echocardiographic integration.
Pulmonary Artery Pressure
In the presence of measurable tricuspid regurgitation, systolic pulmonary artery pressure is calculated based on the peak TR velocity and right atrial pressure estimate. A TR velocity greater than 2.8 m/s is considered to increase the likelihood of pulmonary hypertension, but the final likelihood also depends on RV size, RV function, right atrium, IVC, interventricular septum shape, and pulmonary flow parameters.
How to Formulate a Conclusion
The optimal formulation should include not only 'RV dilated' or 'function reduced' but specific numbers: basal and mid-diameter, TAPSE, S′, FAC, and, if available, 3D-RVEF and RV free-wall strain. If parameters diverge, it is preferable to write an integral assessment: for example, 'RV size increased; longitudinal function by TAPSE preserved, but FAC and strain reduced — signs of RV systolic dysfunction.'
This approach aligns with the logic of ASE 2025: quantitative assessment is mandatory, but the diagnosis of RV dysfunction should not depend on a single measurement, especially with poor acoustic windows, significant TR, post-cardiac surgery, or regional contractility disturbances.
Frequently asked questions
Can RV function be considered normal based solely on TAPSE?
No. TAPSE ≥17 mm is a normal threshold for longitudinal annular motion, but ASE 2025 recommends integrating TAPSE with S′, FAC, 3D-RVEF, and/or strain, as well as with the size of the right chambers and hemodynamics.
Which RV size should be listed first in the protocol?
For routine echocardiography, the most practical is the RV basal diameter in RV-focused A4C; the upper reference is 41 mm. It is advisable to supplement it with the mid-diameter and longitudinal size.
Which RV function indicator is preferable when 3D echocardiography is available?
With good data quality, 3D-RVEF is a more global assessment of systolic function than linear indicators. The practical lower normal threshold is 45%.