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PISA Calculator

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Calculate PISA flow rate from radius and aliasing velocity, plus optional regurgitant orifice area and volume for mitral, aortic, or shunt hemodynamics.

Reviewed by the thecalcu.com team · Last updated July 13, 2026

PISA Radius
cm
Aliasing (Nyquist) Velocity
cm/s
Peak Jet Velocity (optional)
cm/s
Jet VTI (optional)
cm

Set Peak Jet Velocity and Jet VTI to 0 to see the base flow rate only. Supply both to also see effective regurgitant orifice area and regurgitant volume.

PISA Flow Rate

0mL/s
Effective Regurgitant Orifice Area—
Regurgitant Volume—

Informational only. Valve severity grading (mild/moderate/severe) requires integrating multiple echocardiographic parameters and clinical judgment from a qualified provider.

What is a PISA?

The PISA Calculator computes the general proximal isovelocity surface area (PISA) flow rate used in Doppler echocardiography to quantify flow through a regurgitant or shunt orifice. Flow rate equals 2 x pi x radius squared x aliasing velocity, where the PISA radius and aliasing (Nyquist) velocity are read directly off a color Doppler image.

Optionally supplying a peak jet velocity and the jet's velocity-time integral (VTI) also produces the effective regurgitant orifice area and regurgitant volume. For mitral regurgitation severity grading specifically, see the EROA Calculator, which applies this same PISA method with published ASE severity bands.

Why Use a PISA Calculator?

The PISA flow-rate equation involves squaring a radius and multiplying by a velocity, simple individually, but easy to fumble under time pressure during a live echocardiographic study or while reviewing recorded measurements. This calculator returns the flow rate, and if supplied, orifice area and volume, instantly and consistently.

It's useful as a quick hemodynamic reference across multiple valve lesions and shunt types, since the underlying PISA principle is the same regardless of which structure is being assessed.

Who Should Use This Calculator?

Cardiology fellows, sonographers, and echocardiography students learning the PISA method can use this tool to check worked examples against the published flow-rate equation. Clinicians reviewing recorded PISA radius and velocity measurements from a prior study may also use it as a quick calculation reference.

This calculator is strictly for informational and educational purposes and is not a substitute for a full echocardiographic study or a qualified healthcare provider's clinical interpretation of valve or shunt disease.

What Insights Does the PISA Calculator Give You?

PISA Flow Rate is the primary result, the instantaneous flow rate in milliliters per second through the measured orifice, based on the hemisphere radius and aliasing velocity.

Effective Regurgitant Orifice Area appears when a peak jet velocity is supplied, dividing flow rate by that velocity to estimate the functional size of the regurgitant orifice.

Regurgitant Volume appears when a jet velocity-time integral is also supplied, multiplying the orifice area by the VTI to estimate the total volume of regurgitant flow per beat.

How to use this PISA calculator

  1. Measure the PISA Radius from the color Doppler image at the point where the aliasing color change occurs, and enter it in centimeters.
  2. Enter the Aliasing (Nyquist) Velocity shown on the color Doppler scale, typically 20-40 cm/s.
  3. Review the PISA Flow Rate result, shown in milliliters per second.
  4. Optionally, enter the Peak Jet Velocity from continuous-wave Doppler to see the effective regurgitant orifice area.
  5. Optionally, enter the Jet Velocity-Time Integral to see the estimated regurgitant volume.
  6. Cross-check flow rate and orifice area trends against other quantitative measures before drawing any clinical conclusion.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The general PISA flow-rate formula is:

Flow Rate (mL/s) = 2 x π x Radius² (cm) x Aliasing Velocity (cm/s)

When a peak jet velocity is available:

Effective Regurgitant Orifice Area (cm²) = Flow Rate ÷ Peak Jet Velocity

When a velocity-time integral (VTI) is also available:

Regurgitant Volume (mL) = Effective Regurgitant Orifice Area x Jet VTI

Worked example: A PISA radius of 0.8 cm and an aliasing velocity of 40 cm/s give a flow rate of 2 x π x 0.8² x 40 ≈ 160.85 mL/s. If the peak jet velocity is 500 cm/s, the effective regurgitant orifice area is 160.85 ÷ 500 ≈ 0.322 cm²; with a jet VTI of 70 cm, regurgitant volume is 0.322 x 70 ≈ 22.5 mL.

Frequently Asked Questions

What does PISA stand for in echocardiography?
PISA stands for Proximal Isovelocity Surface Area, a Doppler echocardiography method that measures blood flow through a regurgitant or shunt orifice. As blood accelerates toward the orifice, it forms concentric hemispheric shells of constant velocity, and the flow rate through any one shell equals that shell's surface area times its velocity.
What is the general PISA flow rate formula?
Flow rate (mL/s) equals 2 x pi x radius squared x aliasing velocity, where radius is the PISA hemisphere radius in centimeters and aliasing velocity is the color Doppler Nyquist limit in centimeters per second. This is the core hemodynamic principle behind PISA, independent of which valve or shunt is being assessed.
Does this calculator diagnose mitral regurgitation severity?
This tool computes the general PISA flow rate and, optionally, effective regurgitant orifice area and regurgitant volume. For mitral regurgitation severity grading specifically, use the dedicated EROA Calculator, which applies published ASE severity thresholds to the PISA method.
What is aliasing velocity and why does it matter?
Aliasing velocity is the color Doppler Nyquist limit at which the PISA hemisphere is measured, typically set between 20 and 40 cm/s toward the direction of the regurgitant jet. Choosing an appropriate aliasing velocity keeps the PISA radius large enough to measure accurately while still representing the true hemispheric shell.
When are the optional peak velocity and VTI fields needed?
Peak jet velocity is needed to compute effective regurgitant orifice area (ERO), since ERO equals flow rate divided by peak velocity. The jet's velocity-time integral (VTI) is then needed to compute regurgitant volume, since regurgitant volume equals ERO multiplied by VTI. Leave either field at 0 to see the flow rate alone.
Can this method be used for aortic regurgitation or shunts, not just mitral regurgitation?
Yes, the underlying PISA flow-rate equation is a general hemodynamic principle that applies whenever flow accelerates through a discrete orifice, including aortic regurgitation, tricuspid regurgitation, and intracardiac shunts such as a ventricular septal defect. Only the interpretation of severity thresholds differs between valve types.
Why does the PISA radius matter so much in the formula?
Because the formula squares the radius, small measurement errors in radius are magnified in the flow-rate result, a common source of variability in PISA-based assessments. Careful zooming of the ultrasound image and consistent aliasing velocity settings help minimize this error.
Is a bigger flow rate always worse?
Not necessarily on its own, flow rate must be interpreted alongside the peak jet velocity and time-velocity integral to derive orifice area and regurgitant volume, which are the values typically used for severity grading. Flow rate by itself is an intermediate hemodynamic measurement, not a final severity indicator.
How accurate is the PISA method compared to other techniques?
PISA is one of the most widely validated quantitative methods in echocardiography and is recommended by major imaging society guidelines, though it assumes a hemispheric flow convergence shape that isn't always perfectly accurate, especially with eccentric or non-circular orifices. Clinicians often combine it with other measures like vena contracta width for a fuller picture.
What units does this calculator use?
Radius is entered in centimeters, velocities in centimeters per second, and the velocity-time integral in centimeters, consistent with standard echocardiography reporting conventions. Flow rate is returned in milliliters per second, and volume in milliliters.
Is this calculator a substitute for a cardiologist's interpretation?
No, this tool is for informational and educational purposes only and performs the underlying PISA arithmetic; it does not replace a full echocardiographic study or a cardiologist's clinical interpretation of valve disease severity.
How does PISA relate to stroke volume measurements?
PISA and stroke volume are related but distinct, PISA measures instantaneous regurgitant flow through an orifice, while stroke volume (see the Stroke Volume Calculator) measures the total volume ejected by the ventricle each beat, calculated from end-diastolic and end-systolic volumes.
Also known as
PISA flow rate calculatorproximal isovelocity surface area calculatorPISA method calculatorregurgitant orifice area calculatorPISA hemodynamics calculator