🫀 EROA Calculator (PISA Method)
Quantifying valve leaks from the echo numbers.
For informational purposes only, not medical advice. Consult a healthcare professional.
Effective regurgitant orifice area measures the hole a leaky valve behaves like, in square centimeters: EROA = 2πr² × aliasing velocity / peak velocity. A PISA radius of 0.8 cm with aliasing at 40 cm/s and a 500 cm/s jet gives 0.32 cm², moderate-to-severe mitral regurgitation (severe starts at 0.40). Enter your echo numbers.
How to Use This Calculator
PISA (proximal isovelocity surface area) is measured on color Doppler during the echo. The sonographer records the radius of the aliasing shell and the machine gives the velocities.
Enter the PISA radius in centimeters, measured at mid-systole (mitral) or mid-diastole (aortic) on the color Doppler image.
Enter the aliasing velocity (the Nyquist limit set on the machine, often around 30 to 40 cm/s) and the peak velocity of the regurgitant jet from continuous-wave Doppler.
Select the valve. Severity cutoffs differ: severe MR starts at 0.40 cm², severe AR at 0.30 cm². Read your EROA and band.
The PISA Formula
Blood accelerating toward the leak forms hemispheric shells of equal velocity, visible as the aliasing boundary on color Doppler. The flow crossing that shell (its area times the aliasing velocity) must equal the flow through the orifice itself, by conservation of mass. Dividing by the peak jet velocity converts that flow into the orifice area. The hemisphere assumption is the method's known weakness: real shells flatten, especially with eccentric wall-hugging jets, so PISA underestimates those. Three-dimensional vena contracta area is the modern cross-check, but PISA remains the workhorse because it needs only standard Doppler.
Worked Example
Mitral regurgitation: PISA radius 0.8 cm, aliasing velocity 40 cm/s, peak velocity 500 cm/s. Flow = 2π(0.8)²(40) = 2 × 3.1416 × 0.64 × 40 = 160.8 mL/s. EROA = 160.8/500 = 0.32 cm². For the mitral valve that is moderate (severe ≥ 0.40); for the aortic valve the same number would already be severe (≥ 0.30). A larger shell, radius 1.0 cm: flow = 2π(1.0)(40) = 251.3 mL/s, EROA = 0.50 cm², severe by either valve's standard. I verified both against the formula the calculator uses. Note how the radius dominates: EROA grows with the square of r, so a small measurement error in r moves the answer a lot.
Severity Bands
| EROA (cm²) | Mitral | Aortic |
|---|---|---|
| Under 0.20 (MR) / 0.10 (AR) | Mild | Mild |
| 0.20 - 0.39 (MR) / 0.10 - 0.29 (AR) | Moderate | Moderate |
| 0.40+ (MR) / 0.30+ (AR) | Severe | Severe |
These cutoffs come from the ACC/AHA valvular guidelines' integrative criteria. EROA never stands alone clinically: regurgitant volume (EROA times the velocity-time integral), regurgitant fraction, vena contracta width, pulmonary pressures, and chamber sizes all feed the final grade. A "moderate" EROA with a dilated left ventricle and pulmonary hypertension is managed more aggressively than the number alone suggests. Severe asymptomatic MR with a dilating ventricle or falling EF is a surgical conversation even without symptoms, because waiting for symptoms costs myocardium. For the pressures behind these decisions, our blood pressure checker covers systemic pressure, and our ejection fraction calculator is the pump number cardiologists watch as regurgitation progresses.
When PISA Misleads
Eccentric jets that hug the atrial wall flatten the PISA shell and make EROA read falsely small; this is the classic underestimation trap in mitral valve prolapse. Multiple jets cannot be summed from one shell. Very brief or late-systolic jets get over-weighted by a mid-systolic radius. Atrial fibrillation varies the radius beat to beat, so averaging several beats matters. And aliasing velocity choice shifts the radius: set the Nyquist too high and the shell shrinks into noise. The echo lab's final grade integrates all of this, which is why the report's conclusion outranks any single number, including this one.
From EROA to Decisions
Severe primary MR with symptoms is a class I indication for mitral surgery in guidelines; severe asymptomatic MR gets surgery when the ventricle dilates (LVESD ≥ 40 mm) or EF slips toward 60%. Severe AR follows similar logic with its own chamber thresholds. Moderate disease gets surveillance: echos every 6 to 12 months watching for the ventricle to enlarge or pressures to rise. None of these decisions use EROA in isolation, but every one of them starts from quantifying the leak, which is what this number does. Bring the full echo report, rather than only the EROA number, to the cardiology visit.
EROA vs Vena Contracta: The Cross-Check
Guidelines never grade regurgitation from EROA alone, and the vena contracta width is its usual partner: the narrowest neck of the jet just downstream of the orifice. Severe MR shows a vena contracta 0.7 cm or wider; severe AR 0.6 cm or wider. When PISA says 0.35 and the vena contracta says 0.5, the lab believes the anatomy over the arithmetic and calls it moderate, remeasuring rather than averaging. Three-dimensional vena contracta area is the emerging tiebreaker, measuring the orifice directly instead of inferring it from flow. The practical lesson for reading your own report: look for agreement across parameters. Concordant severe markers mean severe disease; discordant ones mean the lab will say "at least moderate" and look harder.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is EROA in cardiology?
Effective Regurgitant Orifice Area: the functional size of the leak in a regurgitant valve, in cm². It is calculated from Doppler echo measurements by the PISA method and is the most load-independent quantifier of regurgitation severity.
What EROA is severe mitral regurgitation?
0.40 cm² or more, per ACC/AHA guidelines. Moderate is 0.20-0.39, mild under 0.20. The grade also weighs regurgitant volume, vena contracta, and chamber remodeling.
What EROA is severe aortic regurgitation?
0.30 cm² or more. Aortic cutoffs run lower than mitral (moderate 0.10-0.29) because diastolic regurgitation fills longer and the thresholds were calibrated separately.
How is EROA measured?
By the PISA method on color Doppler: measure the radius of the aliasing shell converging on the leak, note the aliasing velocity, and divide 2πr²×Va by the peak jet velocity from continuous-wave Doppler.
What is the PISA method?
Proximal Isovelocity Surface Area: blood accelerating into a leak forms hemispheric velocity shells. Measuring one shell's radius lets you compute the flow rate, and dividing by jet velocity gives the orifice area. It assumes a hemispheric shell shape.
Can EROA be wrong?
Yes, mainly underestimation with eccentric wall-hugging jets (flattened shells), multiple jets, or wrong aliasing velocity settings. Guidelines require integrating several parameters, never grading from EROA alone.
What is regurgitant volume vs EROA?
Regurgitant volume (mL/beat) is EROA times the velocity-time integral of the jet: the actual blood volume leaking per beat. Severe MR is ≥60 mL; severe AR ≥60 mL. Volume depends on pressure; EROA is more load-independent.
Does a small EROA ever need surgery?
Rarely for the leak itself, but moderate regurgitation with a dilating ventricle, pulmonary hypertension, or symptoms gets treated on those grounds. Surgery decisions integrate the whole echo, not one number.
How often should moderate regurgitation be followed?
Typically with echocardiography every 6-12 months for moderate disease, watching ventricular size, EF, and pulmonary pressures. Mild disease can go 2-3 years between studies if stable.
Is EROA the same as valve area in stenosis?
No, opposite concepts. EROA quantifies a leak (regurgitation); valve area in stenosis (e.g. by the Gorlin formula) quantifies a narrowing. Both are in cm² but answer different questions.