Mitral Regurgitation Assessment Using the Proximal Isovelocity Surface Area Method

Understanding the Formula Components

• The American College of Cardiology recommends calculating mitral regurgitation regurgitant volume (RVol) using the Proximal Isovelocity Surface Area (PISA) method, where RVol = EROA × VTI, with EROA calculated as 2πr² × aliasing velocity ÷ peak MR velocity, and VTI as the velocity time integral of the MR jet 1, 2
• The Effective Regurgitant Orifice Area (EROA) is calculated as 2πr² × (aliasing velocity ÷ peak MR velocity), where r is the PISA radius measured from the first color alias to the mitral valve orifice 3
• The Velocity Time Integral (VTI) is measured from the continuous-wave Doppler of the MR jet 1

Important Considerations and Limitations

• The PISA method assumes a hemispheric flow convergence geometry, which is rarely the case in secondary MR, leading to potential underestimation 3, 4
• Errors in radius measurement are squared, resulting in large variance in calculated EROA 3
• Single-frame measurements can significantly over or underestimate MR severity, especially in non-holosystolic MR 1, 6

Alternative and Complementary Approaches

• The American College of Cardiology suggests using 3D echocardiography to directly measure EROA and avoid underestimation issues inherent to 2D PISA 3, 5
• The Volumetric Method calculates RVol as the difference between total LV stroke volume and forward stroke volume (LVOT stroke volume) 2, 6

Practical Application Algorithm

• Measure PISA radius (r) using an appropriate aliasing velocity (typically around 30-40 cm/s) and calculate EROA using the formula: EROA = 2πr² × (aliasing velocity ÷ peak MR velocity) 3, 2
• Calculate Regurgitant Volume (RVol) using the formula: RVol = EROA × VTI 3, 1

Common Pitfalls to Avoid

• Single-frame measurement errors can significantly overestimate severity in non-holosystolic MR 1, 7
• Assuming hemispheric flow convergence can lead to underestimation, especially in secondary MR 3, 4
• Neglecting the effect of driving velocity can result in overestimation of MR severity 6
• Relying solely on PISA can lead to inaccurate assessment, and guidelines recommend using multiple parameters to determine MR severity 8, 7