Severe primary MR: the six parameters and what each threshold means
ACC/AHA VHD 2020 defines severe primary MR by integrating multiple findings, not by relying on a single cutoff. Understanding what each threshold means — and how the findings work together — is the foundation for using the Primary MR Severity Tool correctly.
ACC/AHA VHD 2020 defines severe primary MR by integrating multiple findings, not by relying on a single cutoff. Understanding what each threshold means — and how the findings work together — is the foundation for using the Primary MR Severity Tool correctly. The Primary MR Severity Tool integrates up to six parameters to classify MR severity. This page explains what each parameter measures, what the severe threshold means, and why no single number is sufficient on its own.
Key takeaway
Severe primary MR is assessed by integrating six parameters. EROA ≥ 0.40 cm² is the headline quantitative threshold, but it should be interpreted alongside regurgitant volume, regurgitant fraction, vena contracta, pulmonary vein systolic reversal, and qualitative grade.
Key points
- EROA ≥ 0.40 cm² is the main quantitative threshold for severe primary MR, but it is calculated by the PISA method and assumes hemispheric flow convergence.
- Regurgitant volume ≥ 60 mL/beat and regurgitant fraction ≥ 50% are important quantitative corroborators.
- When EROA, regurgitant volume, and regurgitant fraction disagree, review measurement conditions and calculation steps.
- Vena contracta width ≥ 0.70 cm provides an independent structural confirmation that is less dependent on PISA geometry.
- Pulmonary vein systolic flow reversal strongly supports severe MR when present, but its absence does not exclude severe MR.
- ACC/AHA Stage C2 — asymptomatic severe primary MR with LVEF ≤ 60% or LVESD ≥ 40 mm — is an important threshold for intervention decisions.
- In secondary MR, EROA 0.20–0.39 cm² may be clinically important, but this page does not use it as the standalone severe threshold.
When to read this
Read this when you have MR parameters from an echo report and want to understand what each threshold means, how to interpret discordant findings, and how primary and secondary MR differ before entering values into the MR Severity Tools.
The six severe-range parameters
| Parameter | Severe threshold | What it measures | Key limitation |
|---|---|---|---|
| Qualitative color Doppler grade | Severe (visual assessment) | Jet area, density, and origin relative to LA size | Operator-dependent; loading conditions and blood pressure affect jet size; use as corroboration, not as the sole basis |
| EROA (effective regurgitant orifice area) | ≥ 0.40 cm² | Effective cross-sectional area of the regurgitant orifice at the vena contracta | PISA assumes hemispheric flow convergence; less reliable with eccentric, multiple, or non-circular jets |
| Regurgitant volume | ≥ 60 mL/beat | Volume of blood regurgitating per beat | Depends on the accuracy of EROA and MR TVI; interpret carefully in high-output states |
| Regurgitant fraction | ≥ 50% | Proportion of LV stroke volume that regurgitates | Requires accurate total and forward stroke volume estimates; vulnerable to LVOT diameter measurement error |
| Vena contracta width | ≥ 0.70 cm | Narrowest width of the regurgitant jet at the valve level | 2D measurement is limited with non-circular orifices; 3D assessment may be more accurate |
| Pulmonary vein systolic flow reversal | Present | Retrograde systolic flow in the pulmonary veins caused by elevated LA pressure | Specific when present, but not sensitive; many patients with severe MR do not show reversal |
Primary MR severity ranges: mild, moderate, and severe
| Parameter | Mild | Moderate | Severe | Key limitation |
|---|---|---|---|---|
| EROA | < 0.20 cm² | 0.20–0.39 cm² | ≥ 0.40 cm² | Depends on PISA; error-prone with eccentric jets or non-circular orifices |
| Regurgitant volume | < 30 mL/beat | 30–59 mL/beat | ≥ 60 mL/beat | Depends on the accuracy of EROA and MR TVI |
| Regurgitant fraction | < 30% | 30–49% | ≥ 50% | Requires accurate total and forward stroke volume measurements |
| Vena contracta width | < 0.30 cm | 0.30–0.69 cm | ≥ 0.70 cm | 2D measurement is limited with non-circular orifices |
| Pulmonary vein systolic flow | Usually forward systolic flow | May be blunted | Systolic flow reversal present | Strong supportive finding when present, but absence does not exclude severe MR |
| Qualitative grade | Mild | Moderate | Severe | Operator-dependent; do not use as the sole basis for grading |
How to integrate discordant parameters
In straightforward severe primary MR, most parameters point in the same direction: EROA ≥ 0.40 cm², regurgitant volume ≥ 60 mL/beat, regurgitant fraction ≥ 50%, and vena contracta ≥ 0.70 cm.
When parameters disagree — for example, EROA 0.42 cm² with regurgitant volume 48 mL/beat — the first step is not to choose one value, but to determine why they disagree.
Common causes include PISA radius measurement conditions, aliasing velocity settings, high-output states, LVOT diameter error, eccentric jets, multiple jets, and technically limited images. When findings are discordant, review measurement quality and corroborate with other parameters when possible.
Secondary MR: what is the same and what is different
In secondary MR, regurgitation is caused not by primary leaflet destruction but by LV dilation, papillary muscle displacement, leaflet tethering, and impaired coaptation. For the same regurgitant volume, clinical meaning can differ depending on LV size, forward stroke volume, and heart failure status.
In this tool, the standalone severe diagnostic thresholds for secondary MR remain EROA ≥ 0.40 cm², regurgitant volume ≥ 60 mL/beat, and regurgitant fraction ≥ 50%. These are treated as the same severe diagnostic thresholds used for primary MR.
However, in secondary MR, EROA 0.20–0.39 cm² can still be clinically and prognostically important in patients with heart failure. This does not mean it is "safe moderate MR." But it also should not be treated as the standalone severe threshold in this tool.
- EROA ≥ 0.40 cm² supports severe MR
- EROA 0.20–0.39 cm² is an intermediate range that may be clinically important in secondary MR
- EROA < 0.20 cm² is usually in the mild range, but must be interpreted with other findings
Secondary MR severity should be interpreted by integrating EROA, regurgitant volume, regurgitant fraction, vena contracta, pulmonary venous flow, LV remodeling, tethering, and the heart failure state.
Secondary MR severity ranges: mild, moderate, and severe
| Parameter | Mild | Moderate | Severe | Key limitation |
|---|---|---|---|---|
| EROA | < 0.20 cm² | 0.20–0.39 cm² | ≥ 0.40 cm² | In secondary MR, 0.20–0.39 cm² may be clinically important, but it is not used here as the standalone severe threshold |
| Regurgitant volume | < 30 mL/beat | 30–59 mL/beat | ≥ 60 mL/beat | Influenced by LV size, forward flow, and measurement conditions |
| Regurgitant fraction | < 30% | 30–49% | ≥ 50% | Depends on forward stroke volume and measurement accuracy |
| Vena contracta width | < 0.30 cm | 0.30–0.69 cm | ≥ 0.70 cm | Elliptical or multiple jets in secondary MR may cause under- or overestimation |
| Pulmonary vein systolic flow | Usually forward systolic flow | May be blunted | Systolic flow reversal present | Affected by LA compliance and atrial fibrillation; not always assessable |
| LV remodeling / tethering | — | May be present | Important for interpretation | In secondary MR, interpret severity with LV dilation, tethering, and impaired coaptation |
Stage classification in severe primary MR
| Stage | Symptoms | LV parameters | Intervention implication |
|---|---|---|---|
| B (Progressive) | None | LVEF ≥ 60% AND LVESD < 40 mm | Surveillance; no intervention unless other triggers |
| C1 (Severe asymptomatic — preserved LV) | None | LVEF ≥ 60% AND LVESD < 40 mm | Class IIa if repair very likely durable and at experienced center; otherwise surveillance |
| C2 (Severe asymptomatic — LV dysfunction) | None | LVEF ≤ 60% OR LVESD ≥ 40 mm | Class I indication — intervention recommended |
| D (Severe symptomatic) | Present (dyspnea, fatigue, reduced exercise tolerance) | Any LVEF, any LVESD | Class I indication — intervention recommended |
Why LVEF 60% is the staging threshold
In severe primary MR, the chronic volume overload of the regurgitant fraction dilates the LV and inflates apparent LVEF. An LVEF of 55% that would represent borderline preserved function in other conditions may reflect genuine contractile dysfunction in the volume-loaded MR heart. ACC/AHA VHD 2020 defines LV impairment in this setting as LVEF ≤ 60% — and the boundary is inclusive. LVEF of exactly 60% is Stage C2, not C1.
LVESD ≥ 40 mm
LVESD is an afterload-independent structural marker of LV performance. LVESD ≥ 40 mm indicates that the LV has lost the ability to empty to a normal size even with preserved EF — a sign of subclinical dysfunction. LVESD ≥ 40 mm places a patient in Stage C2 regardless of LVEF. The threshold is inclusive: LVESD of exactly 40 mm is C2.
Body size and EROA: the threshold is not fully indexed
EROA ≥ 0.40 cm² was derived from studies in mixed-size populations. In a small woman with body surface area of 1.5 m², an EROA of 0.35 cm² with regurgitant volume of 54 mL/beat may represent a more significant hemodynamic burden than in a large man. EROA values near threshold should be interpreted alongside regurgitant fraction, regurgitant volume, symptoms, and LV and LA response — not taken as a hard cutoff.
- Otto CM, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. J Am Coll Cardiol. 2021;77(4):e25-e197.
- Zoghbi WA, et al. Recommendations for Noninvasive Evaluation of Native Valvular Regurgitation. J Am Soc Echocardiogr. 2017;30(4):303-371.
Related valve learning
Apply this in practice
Enter the six parameters in the Primary MR Severity Tool for integrated grade and stage classification.
Primary MR Severity Tool