How this calculator works
PISA means proximal isovelocity surface area. This page models a hemispherical shell, multiplied by a convergence-angle factor of angle/180 degrees. At 180 degrees it is a full hemisphere. Flow divided by the matching orifice velocity gives effective area. The same conservation equation can describe a valve opening, but correct timing and geometry must be established by the operator. The result is an estimate for information only and is not medical advice.
Formula
Surface(cm²) = 2πr² × α/180°. Flow(mL/s) = surface × Va. Effective area = Flow/Vmax; integrated volume = effective area × VTI.
Worked example
At radius 0.8 cm and 180°, surface is 4.0212 cm². With Va 40 and Vmax 500 cm/s, effective area is 0.3217 cm². A 90° angle halves these areas and flow.
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Frequently asked questions
Why add an angle?
An idealized constrained convergence region may occupy less than a hemisphere; the angle factor makes that assumption explicit.
Is the calculated volume always regurgitant volume?
Only when the inputs describe a regurgitant jet. For forward valve flow it describes the corresponding integrated forward volume.
Does angle correction solve all geometry errors?
No. Non-spherical contours and time-varying flow remain limitations.