EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)
Use the PISA (Proximal Isovelocity Surface Area) method to quantify valvular regurgitation: enter the PISA radius, aliasing velocity, and peak jet velocity to calculate the EROA and grade mitral regurgitation severity.
cm
cm/s
cm/s
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Severity: Moderate — ASE/EACVI 2017 thresholds: <0.20 mild, 0.20–0.39 moderate, ≥0.40 severe
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Radius squared
0.8 × 0.8 = 0.64 - 2
2π × r²
2 × π × 0.64 = 4.0212 - 3
EROA (cm²)
4.0212 × 40 ÷ 500 = 0.322PISA method: flow rate at aliasing shell divided by peak jet velocity.
How does this calculator work?
EROA (cm²) = 2π × r² × Va / Vmax using colour-Doppler PISA on echocardiography. Mitral regurgitation is mild (<0.20 cm²), moderate (0.20–0.39 cm²), or severe (≥0.40 cm²) per ASE/EACVI 2017. Multiply EROA by CW Doppler VTI for regurgitant volume per beat. Method assumes a hemispheric isovelocity surface at the Nyquist aliasing velocity.
Formula
How this is calculated
The effective regurgitant orifice area (EROA) quantifies the functional cross-section of a regurgitant valve — most commonly the mitral valve — through which blood leaks backward. The PISA method exploits the conservation of mass: as blood accelerates toward a regurgitant orifice, it forms concentric hemispheric shells of equal velocity (isovelocity surfaces). The innermost aliasing shell, visible on colour Doppler at the Nyquist velocity Va and radius r, has a flow rate of 2π × r² × Va. Dividing by the peak continuous-wave Doppler velocity Vmax gives EROA. Multiplying EROA by the velocity-time integral (VTI) of the regurgitant jet yields the regurgitant volume per heartbeat.
The 2017 ASE/EACVI joint guideline classifies primary mitral regurgitation as mild (EROA < 0.20 cm²), moderate (0.20–0.39 cm²), or severe (≥ 0.40 cm²). Regurgitant volume thresholds parallel these: severe MR is ≥ 60 mL/beat. The same PISA formula applies to aortic regurgitation (severe ≥ 0.30 cm²) and tricuspid regurgitation (severe ≥ 0.40 cm²) with the respective peak-jet velocity and VTI from CW Doppler.
The PISA method assumes a perfect hemisphere and a flat, circular orifice. Eccentric or wall-hugging jets, non-circular orifices (e.g. commissural MR), heavily calcified valves, and a Nyquist limit set too high or too low all introduce measurement error. Always interpret EROA alongside vena contracta width, jet area, pulmonary vein flow reversal, and clinical context.
Frequently asked questions
Most laboratories set the Nyquist limit to 30–60 cm/s (often 40 cm/s) so the aliasing hemisphere is clearly visible at a radius of 0.5–1.5 cm. A radius below 0.5 cm is too small to measure accurately; above 2 cm the hemispheric assumption breaks down. If the first alias is too close or too far from the orifice, shift the colour-baseline to adjust the Nyquist limit rather than changing the scale.
Zoom in on the regurgitant orifice in the parasternal long-axis or apical four-chamber view, set the frame rate high, and freeze at the frame with the largest visible PISA hemisphere. Measure from the face of the leaflets (anatomical orifice) to the outer edge of the first aliasing contour — this is r. Use at least three measurements and average them.
The method underestimates EROA when the regurgitant jet is eccentric (central PISA forms incompletely), when there are multiple jets, or when the orifice is elongated rather than round. It overestimates when flow constraint near the wall creates a non-hemispheric shape. In these situations, integrate EROA with vena contracta, pulmonary vein reversal, and quantitative Doppler to reach a final grade.
Also known as
TG we-Calculate Editorial Team. (2026). EROA Calculator — Effective Regurgitant Orifice Area (PISA Method) [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/eroa-calculator
TG we-Calculate Editorial Team. "EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)." TG we-Calculate. 2026. https://we-calculate.com/calculator/eroa-calculator.
TG we-Calculate Editorial Team, "EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/eroa-calculator
@misc{wecalculate_eroa_calculator, title = {EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/eroa-calculator}}, year = {2026}, note = {TG we-Calculate} }
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