EROA Mitral Regurgitation Calculator
Enter your echocardiographic measurements to calculate the Effective Regurgitant Orifice Area (EROA), volume flow rate, and regurgitant volume using the validated PISA (Proximal Isovelocity Surface Area) method. The calculator grades severity against both primary (degenerative) and secondary (functional) mitral regurgitation thresholds from ACC/AHA and ASE guidelines.
What is EROA and why does it matter?
The Effective Regurgitant Orifice Area (EROA) is the cross-sectional area of the regurgitant orifice through which blood leaks backward from the left ventricle into the left atrium during systole. It is considered the most reliable single quantitative index of mitral regurgitation (MR) severity because it directly reflects the anatomical size of the leak, independent of loading conditions that affect jet length or area on colour Doppler. An EROA of 0.40 cm² or more denotes severe primary MR by ACC/AHA and ASE guidelines, whereas severe secondary (functional) MR is defined at the lower threshold of 0.30 cm² because, in the context of heart failure and reduced LV function, even smaller degrees of regurgitation carry greater haemodynamic consequences.
How the PISA method works
The Proximal Isovelocity Surface Area (PISA) technique exploits a fundamental principle of fluid dynamics: as blood approaches a narrow orifice it accelerates, forming concentric shells of equal velocity (isovelocity surfaces) that approximate a hemisphere. On colour Doppler, the aliasing velocity (the point at which the colour scale "wraps around") identifies the radius of one of these shells. The volume flow rate at that shell equals the surface area of the hemisphere (2 * pi * r^2) multiplied by the aliasing velocity (Va). Dividing that flow rate by the peak MR velocity from continuous-wave Doppler gives the EROA. Multiplying the EROA by the velocity-time integral (VTI) of the MR jet then yields the regurgitant volume per heartbeat.
Step-by-step measurement guide
Obtain an apical four-chamber or apical long-axis view. Activate colour Doppler and zoom in on the mitral valve. Shift the colour-flow baseline toward the direction of regurgitation (downward for a posteriorly directed jet) until a clear hemisphere of uniform colour appears on the ventricular side of the valve. Reduce the Nyquist limit to 35-45 cm/s - the boundary of the hemisphere is your aliasing velocity (Va). Measure the PISA radius (r) from the centre of the orifice to the outer edge of the hemisphere at mid-systole. Then switch to continuous-wave Doppler aligned with the MR jet to measure peak MR velocity (Vmax) and trace the VTI. Enter all four values here to calculate EROA and regurgitant volume.
Clinical context and limitations
EROA derived by PISA is well validated for central, circular, single orifices. Accuracy decreases with eccentric jets (which do not form true hemispheres), multiple regurgitant orifices (e.g., after repair), non-planar valves, or very small PISA hemispheres at low aliasing velocities. The method also underestimates when the orifice is elliptical, as in functional MR, where 3D colour Doppler vena contracta area (VCA) may provide superior estimates. Because MR severity is a continuum and no single parameter is perfect, guidelines recommend integrating EROA with regurgitant volume, regurgitant fraction, vena contracta width, qualitative jet assessment, LV and LA size, and clinical symptoms before making management decisions.
Mitral regurgitation severity thresholds (ACC/AHA and ASE)
| MR type | Grade | EROA (cm²) | RVol (mL/beat) | RF (%) |
|---|---|---|---|---|
| Primary | Mild | <0.20 | <30 | <30 |
| Primary | Moderate | 0.20-0.29 | 30-44 | 30-39 |
| Primary | Moderate-severe | 0.30-0.39 | 45-59 | 40-49 |
| Primary | Severe | >=0.40 | >=60 | >=50 |
| Secondary | Mild | <0.20 | <30 | <30 |
| Secondary | Moderate | 0.20-0.29 | 30-44 | 30-44 |
| Secondary | Severe | >=0.30 | >=45 | >=50 |
Primary MR uses a higher EROA cutoff for severe (0.40 cm²) than secondary MR (0.30 cm²), reflecting different haemodynamic consequences.
Frequently asked questions
What does EROA stand for?
EROA stands for Effective Regurgitant Orifice Area. It is the functional cross-sectional area through which blood leaks backwards across the mitral valve during systole. A larger EROA means a bigger leak and more severe mitral regurgitation.
What is the PISA method in echocardiography?
PISA stands for Proximal Isovelocity Surface Area. It is a colour Doppler technique that uses the principle of flow convergence: as blood accelerates toward a narrow orifice it forms concentric hemispherical shells of equal velocity. By measuring the radius of the shell at the aliasing boundary and knowing the aliasing velocity, you can calculate the regurgitant flow rate and from that derive EROA and regurgitant volume.
What EROA value indicates severe mitral regurgitation?
For primary (degenerative) MR, an EROA of 0.40 cm² or more with a regurgitant volume of 60 mL/beat or more is classified as severe by ACC/AHA and ASE guidelines. For secondary (functional) MR - caused by LV dysfunction rather than leaflet disease - the threshold for severe is lower: EROA of 0.30 cm² or more and regurgitant volume of 45 mL/beat or more, because even smaller regurgitant volumes worsen outcomes in heart failure patients.
Why does my PISA radius affect the result so much?
EROA is proportional to the square of the PISA radius (r^2). A small measurement error, say 1 mm, therefore produces a much larger proportional error in EROA than a comparable error in velocity. This is why guidelines recommend measuring the PISA radius at mid-systole, from the colour-change boundary to the centre of the regurgitant orifice, and averaging two to three measurements for reproducibility.
What is regurgitant volume and how is it calculated from EROA?
Regurgitant volume (RVol) is the total volume of blood that leaks backward per heartbeat. It is calculated as EROA multiplied by the velocity-time integral (VTI) of the MR jet on continuous-wave Doppler. For example, an EROA of 0.40 cm² with an MR VTI of 150 cm gives a regurgitant volume of 60 mL/beat, which is the threshold for severe primary MR.
Can this calculator be used for aortic or tricuspid regurgitation?
The PISA formula (VFR = 2*pi*r^2 * Va; EROA = VFR / Vmax) is the same for any regurgitant valve, but the severity thresholds and the echocardiographic windows used for measurement differ. This tool applies the mitral regurgitation grading criteria from ACC/AHA and ASE guidelines. For aortic regurgitation or tricuspid regurgitation, different cutoffs and dedicated assessment parameters are used.
What are the main limitations of the PISA method?
The PISA method assumes the flow-convergence zone is a true hemisphere. This assumption breaks down with eccentric jets, non-circular orifices, multiple jets, or when the PISA radius is very small (under about 5 mm). Functional MR often has an elliptical rather than circular orifice, causing PISA-derived EROA to underestimate the true regurgitant orifice area. Three-dimensional echocardiographic vena contracta area measurement is considered more accurate in these situations.