Echocardiographic Assessment of Aortic Regurgitation: BSE 2025 Guide
What the BSE 2025 Practical Guide Changed
The 2025 British Society of Echocardiography document on aortic regurgitation assessment is an applied algorithm for standard transthoracic echocardiography, not just a list of thresholds. The key idea of the consensus is that AR severity is established multiparametrically, considering the mechanism of regurgitation, jet geometry, Doppler signs of regurgitant volume, and LV remodeling. Reference to the original source: BSE practical guideline, 2025.
In practice, this means first confirming the presence of AR and its mechanism, then distinguishing clearly mild regurgitation from significant, and for moderate and severe AR, using several independent signs. It is especially important not to overestimate eccentric jets by color area and not to underestimate acute severe AR with a non-dilated LV.
Minimal Scanning Protocol
Assessment begins with 2D anatomy: number of cusps, calcification, prolapse, restriction, perforation, dilation of the root or ascending aorta, signs of endocarditis or dissection. Parasternal long and short axes, apical 5- and 3-chamber views, and suprasternal access for the arch and descending aorta are mandatory. Color Doppler is performed with an optimized scale, with the BSE document indicating a Nyquist range of about 50–60 cm/s for jet assessment.
CW Doppler is recorded in the direction of the AR jet from multiple windows, as an eccentric jet easily gives an incomplete spectrum. PW Doppler is needed to assess diastolic reversal in the descending and abdominal aorta, as well as for quantitative calculations of volumes through the outflow tracts.
Threshold Values for AR Severity
| Parameter | Mild AR | Moderate AR | Severe AR |
|---|---|---|---|
| Vena contracta, width | <0.3 cm | 0.3–0.6 cm | >0.6 cm |
| Jet width / LVOT diameter | <25% | 25–64% | ≥65% |
| Pressure half-time | >500 ms | 200–500 ms | <200 ms |
| EROA | <0.10 cm² | 0.10–0.29 cm² | ≥0.30 cm² |
| Regurgitant volume | <30 ml | 30–59 ml | ≥60 ml |
| Regurgitant fraction | <30% | 30–49% | ≥50% |
| Flow in descending aorta | None or brief early diastolic reversal | Intermediate pattern | Holodiastolic reversal, end-diastolic velocity >20 cm/s |
The table reflects thresholds presented in the BSE 2025 practical guideline. When parameters diverge, priority is given to the most reliable signs for the given anatomy: vena contracta and quantitative indicators with good visualization, reversal in the aorta when significant chronic AR is suspected, as well as LV size and function as a marker of chronic volume overload.
Color Doppler: Useful, but Not by Jet Area
Color Doppler answers where the jet starts, how central or eccentric it is, and whether vena contracta can be measured accurately. Jet width in LVOT and the jet width/LVOT diameter ratio are mainly applicable for central jets. In eccentric AR, the jet adheres to the wall, changes shape, and may appear smaller or larger than the true regurgitant volume.
Vena contracta is measured at the narrowest part of the jet just distal to the regurgitant orifice. A value <0.3 cm supports mild AR, >0.6 cm — severe. If the jet is multiple, highly eccentric, or the orifice is not round, linear vena contracta becomes less reliable; then integration with PISA, volume calculations, and aortic flow reversal is needed.
CW Doppler and Pressure Half-Time
The CW spectrum of AR is evaluated by signal density and the slope of the diastolic gradient. In severe AR, the spectrum is usually dense, and the pressure half-time is shortened: <200 ms. In mild AR, PHT is usually >500 ms. However, this parameter depends not only on regurgitant volume but also on aortic diastolic pressure, LV compliance, acuteness of the process, and medication hemodynamics.
Therefore, a short PHT should not automatically mean severe chronic AR without confirmation by other signs. In acute severe AR, PHT can be very short due to rapid pressure equalization, while the LV has not yet dilated.
Diastolic Reversal in the Aorta
PW Doppler in the descending thoracic or abdominal aorta is one of the most practical independent signs of significant AR. Severe AR is characterized by holodiastolic reversal. In the BSE guideline, severity is supported by an end-diastolic reversal velocity >20 cm/s in the descending aorta.
A brief early diastolic reversal can occur in mild AR and is not by itself equal to severe regurgitation. It is important to correctly position the sample volume, avoid angular error, and distinguish true diastolic reversal from artifacts or arch branch flows.
Quantitative Assessment: EROA, Volume, and Fraction
Quantitative assessment is especially needed in moderate or potentially severe AR. According to BSE, severe AR corresponds to EROA ≥0.30 cm², regurgitant volume ≥60 ml, and regurgitant fraction ≥50%. Mild AR — EROA <0.10 cm², volume <30 ml, and fraction <30%.
The PISA method requires a clear convergence hemisphere and correct beam direction. Errors in the PISA radius drastically change the result, so with poor orifice geometry or multiple jets, the method should be interpreted cautiously. An alternative is calculating stroke volumes through the LVOT and another valvular tract, but it is sensitive to measurement errors of diameters and VTI.
The Role of LV and Aorta in Final Grading
Chronic severe AR is usually accompanied by LV volume overload: increased end-diastolic and end-systolic dimensions, increased stroke volume, then reduced systolic function. Absence of LV dilation makes chronic severe AR less likely but does not exclude acute AR or early disease phase.
Aortic assessment is mandatory because the AR mechanism is often related to dilation of the root, sinotubular junction, or ascending aorta. The protocol should separately describe the cusps and aortic root: this affects the mechanism, reproducibility of dynamic observation, and choice of surgical tactics.
Complex Situations
Eccentric jet. Do not use the color spot area as the main criterion. Vena contracta, aortic reversal, quantitative indicators, and LV are needed.
Acute AR. The LV may be normal in size, but the clinical picture is severe. Supporting signs: dense short CW jet, short PHT, premature mitral valve closure, significant increase in LV diastolic pressure by indirect signs.
Multiple jets. Linear measurements of one vena contracta may underestimate total regurgitation. An integral assessment is needed, and if transthoracic visualization is insufficient, transesophageal echocardiography.
Associated valvular defects. Calculating regurgitant volume through stroke volume differences becomes less reliable if there is significant mitral regurgitation or shunts. In such cases, greater weight is given to direct AR signs and aortic reversal.
Practical Conclusion Algorithm
- Indicate the mechanism: valvular, root/aortic, or mixed.
- Describe the jet: central, eccentric, single, or multiple.
- Provide key measurements: vena contracta, jet width/LVOT for central jet, PHT, presence and velocity of holodiastolic reversal.
- If AR is more than mild — add EROA, regurgitant volume, and fraction, if methodologically possible.
- Describe LV response and aortic dimensions.
- Formulate the final degree: mild, moderate, or severe, indicating which signs agree and which are limited.
The optimal formulation for severe AR should not sound like "severe by color," but as an integral conclusion: for example, wide vena contracta, quantitative indicators in the severe range, and holodiastolic reversal in the descending aorta. This approach aligns with the practical algorithm of BSE 2025.
Frequently asked questions
Can AR severity be determined solely by the color jet area?
No. BSE 2025 emphasizes a multiparametric approach. The jet area depends on color Doppler settings, pressure, eccentricity, and the wall-adherence (Coanda) effect.
What is the most practical sign of severe AR at the bedside?
A reliable independent sign is holodiastolic reversal in the descending aorta, especially with an end-diastolic velocity >20 cm/s, in combination with other signs of severe AR.
Why can the LV be normal in size in severe acute AR?
LV dilation is a sign of chronic volume overload. In acute AR, remodeling has not yet occurred, so severity should be assessed by Doppler and hemodynamic signs, not just LV size.