π« PISA Calculator
Quantify mitral regurgitation from echo measurements.
For informational purposes only, not medical advice. Consult a healthcare professional.
The proximal isovelocity surface area method turns a color Doppler image into a number for mitral regurgitation severity. As blood accelerates toward the leaking valve, it forms concentric shells of equal velocity; the shell where color aliases gives a measurable radius. Multiplying the shell surface area by the aliasing velocity yields the regurgitant flow rate, and dividing by the peak jet velocity gives the effective regurgitant orifice area, or EROA. This calculator runs that chain for teaching and echo-lab reference.
How to Use This Calculator
Enter the three echo measurements from the PISA study: the flow convergence radius, the aliasing velocity, and the peak regurgitant jet velocity.
Measure the PISA radius in centimeters at mid-systole on the flow convergence hemisphere, with the aliasing velocity noted.
Enter the aliasing velocity in cm/s from the color Doppler settings and the peak MR jet velocity in cm/s from continuous-wave Doppler.
Read the effective regurgitant orifice area in cm2 and the severity grade by standard cutoffs.
How the Math Works
Flow rate equals 2 times pi times radius squared times the aliasing velocity: the surface area of a hemisphere times the velocity crossing it. Dividing flow rate by the peak MR velocity gives EROA in cm2. With radius 0.8 cm, aliasing 40 cm/s, and peak velocity 500 cm/s, flow is 2 times 3.1416 times 0.64 times 40, about 161 mL/s, and EROA is 161 divided by 500, about 0.32 cm2. Severity cutoffs for primary mitral regurgitation are under 0.2 mild, 0.2 to 0.39 moderate, and 0.4 or above severe; secondary MR uses lower thresholds around 0.2 for severe.
Worked Example
With a PISA radius of 0.8 cm, aliasing velocity 40 cm/s, and peak jet velocity 500 cm/s, the regurgitant flow rate is about 161 mL/s and the EROA is 0.32 cm2. The calculator grades this as Moderate for primary mitral regurgitation, since 0.32 sits between the 0.2 and 0.4 cutoffs. The same radius with a lower aliasing velocity would shrink the EROA, which is why the color scale setting is part of the measurement.
Reading Your Result
Mild EROA under 0.2 generally means routine surveillance. Moderate 0.2 to 0.39 calls for closer follow-up with attention to symptoms, left ventricular size, and pulmonary pressures. Severe at 0.4 or above, especially with symptoms or LV dilation, is the range where valve intervention is discussed per guidelines. PISA assumes a hemispheric, central jet; eccentric wall-hugging jets and multiple jets break the assumption and need other quantification methods.
| EROA (primary MR) | Grade | Typical management |
|---|---|---|
| Under 0.20 cm2 | Mild | Routine surveillance |
| 0.20-0.39 cm2 | Moderate | Closer follow-up |
| 0.40+ cm2 | Severe | Consider intervention if symptomatic |
Limitations
PISA is an echo-lab measurement requiring proper image acquisition; garbage in means garbage out. It assumes a single central hemispheric convergence zone, and fails with eccentric jets, very small or very large orifices, and MR that varies through systole. Severity grading integrates many parameters beyond EROA, including regurgitant volume, vena contracta, and chamber remodeling. This is a teaching tool for clinicians and sonographers, not a diagnostic device.
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For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the PISA method?
A Doppler echo technique that quantifies valve leaks by measuring the hemisphere of accelerating blood flow on the upstream side of the regurgitant orifice. The radius of the color-aliasing shell, combined with velocities, yields flow rate and effective orifice area. It is the most widely used quantitative method for mitral regurgitation.
What is EROA?
Effective regurgitant orifice area: the functional size of the leak in cm2, derived from flow divided by velocity. Unlike the anatomical hole, it reflects how the valve actually behaves under pressure. Larger EROA means more severe regurgitation.
What EROA means severe mitral regurgitation?
0.40 cm2 or more for primary (degenerative) MR. For secondary (functional) MR, thresholds are lower, around 0.20 cm2 for severe, because the ventricle tolerates less. Always note which etiology the cutoffs apply to.
What is aliasing velocity?
The color Doppler velocity scale setting at which colors flip, marking the shell of known velocity used for the radius measurement. Typical PISA studies set it around 30 to 40 cm/s. The measured radius depends on this setting, so it must be recorded with the result.
Why does the jet need to be central?
The math assumes blood converges in a neat hemisphere toward the orifice. Eccentric wall-hugging jets flatten the convergence zone and violate the geometry, making EROA unreliable. Multiple jets need separate or alternative quantification.
What is regurgitant volume?
EROA multiplied by the velocity-time integral of the regurgitant jet: the actual milliliters leaking per beat. Severe primary MR is typically 60 mL or more per beat. It pairs with EROA to describe severity in volume terms patients grasp more easily.
Can PISA assess aortic regurgitation?
In principle yes, but practice favors other methods for the aortic valve because the convergence geometry is less reliable there. PISA is most validated and most used for mitral regurgitation.
How accurate is PISA?
Good in experienced hands for central jets, with known pitfalls: it overestimates with non-hemispheric convergence and underestimates very eccentric jets. Guidelines recommend integrating several parameters rather than trusting any single number, which is honest advice for every echo measurement.
Does blood pressure affect the measurement?
Yes. Higher driving pressure increases regurgitant flow for the same orifice, so EROA is more load-independent than the color jet area but not fully load-independent. Note the blood pressure alongside the study for fair comparisons over time.
When is mitral valve surgery considered?
Guidelines weigh symptoms, LV size and function, pulmonary hypertension, atrial fibrillation, and quantified severity together. Severe MR with symptoms or LV dilation generally prompts intervention discussion; asymptomatic severe MR is watched closely with defined triggers. The EROA is one input among many.