Tools for Echocardiographic Calculations

Muhamed Saric, MD, PhD
New York University



To calculate effective orifice area (EOA) of an orifice assumed to be circular in shape and located on a planar surface. The PISA method can be used to calculate the area of a stenotic, regurgitant or shunt orifice. Once the EOA is known, one can calculate the stroke volume across the orifice; in regurgitant lesion, this the regurgitant volume.

Technical Hints

If you shift the baseline of the Nyquist color scale, the upper and the lower Nyquist limits will not be the same. In such instances, use the Nyquist limit that is in the direction of measured flow. Anagle correcton is used for mitral stenosis only.


PISA radius (r):  


Aliasing velocity (Valias; Nyquist limit)


Maximum velocity (Vmax):


PISA angle:


Velocity-time integral  cm


EOA (uncorrected)  cm2
Regurgitant volume  mL

EOA (angle corrected):



EOA = 2 * pi * r2 * (Valias / Vmax)

Regurgitant volume = EOA * VTI


Mitral stenosis: Circulation 1993;88:1157-65
Atrial septal defect: Circulation 1993;87:1591-1603
Tricuspid regurgitation: Am Heart J 1994;127:1354-62
Mitral regurgitation: J Am Coll Cardiol 1995;25:703-709
Aortic regurgitation:  J Am Coll Cardiol 1998;32:1032-1039