Assessment of Mitral Regurgitation Severity: PISA, EROA, and Vena Contracta — A Practical Algorithm
PISA Method and EROA Calculation
The PISA method is based on identifying flow convergence hemispheres by lowering the Nyquist limit in the direction of flow to 20–40 cm/s (BSE, mitral valve assessment guidelines, 2021). The PISA radius is measured at its maximum height, after which the effective regurgitant orifice area (EROA) is calculated. The method assumes a circular regurgitant orifice with a hemispherical geometry of flow convergence zones.
During intraprocedural assessment of functional MR (ASE, 2022), for EROA calculation using the PISA method, the color Doppler baseline is shifted towards the regurgitant flow, and the PISA shell radius is measured from the vena contracta to the color change point (in the given example — from yellow to blue).
Regurgitant Volume via Continuity Equation
After calculating EROA and tracing the CW signal of MR for VTI measurement, the continuity equation is applied to calculate the regurgitant volume (BSE, 2021).
Limitations of the Method
The accuracy of EROA calculation using the PISA method is limited in cases of multiple and eccentric jets (according to BSE for aortic regurgitation, 2025; the principle applies to PISA assessment). EROA obtained by the 2D PISA method underestimates the regurgitant orifice area compared to the 3D PISA method (ASE, 2023). In atrial fibrillation with significant variability in cardiac cycle duration or rapid ventricular response, many of these indices become less reliable (ASE, 2023).
Vena Contracta and 3D Methods
Vena contracta and derived PISA indices (EROA and regurgitant volume) can be calculated and summed in cases of multiple jets (ASE, 2019). For quantitative assessment, the vena contracta area (VCA) method using 3D color Doppler is considered presumably more suitable, although it is not yet sufficiently validated (ASE, 2019). After edge-to-edge procedures (M-TEER), assessment methods require additional validation due to known limitations of both color Doppler jet characteristics and quantitative methods (ASE, 2019).
Specific threshold values for EROA and vena contracta for grading the severity of native MR are not provided in the given excerpts — [to clarify].
Frequently asked questions
To what Nyquist limit should the scale be lowered for measuring the PISA radius in MR?
According to BSE (2021), the Nyquist limit is lowered in the direction of flow to 20–40 cm/s, then the PISA radius is measured at its maximum height.
When does the PISA method lose accuracy?
In cases of multiple and eccentric jets, the EROA calculation using the PISA method is limited. The method is also inaccurate with non-circular orifices, as it assumes a circular orifice and hemispherical flow geometry.
How is the PISA radius measured during intraprocedural assessment of functional MR?
According to ASE (2022), the color Doppler baseline is shifted towards the regurgitant flow, and the PISA radius is measured from the vena contracta to the color change point.
Do EROA values differ between 2D and 3D PISA?
Yes. According to ASE (2023), EROA obtained by the 2D PISA method underestimates the regurgitant orifice area compared to the 3D PISA method.
How reliable are PISA/EROA indices in atrial fibrillation?
In atrial fibrillation with significant variability in cycle duration or rapid ventricular response, many of these indices become less reliable (ASE, 2023).