PISA Method for Mitral Regurgitation (MR)

PISA Method for Mitral Regurgitation (MR)

Concept (Flow Convergence Principle)

The PISA (Proximal Isovelocity Surface Area) method is based on the formation of hemispheric shells of equal velocity proximal to a regurgitant orifice. As blood accelerates toward the mitral valve during systole, it forms concentric hemispheres.

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Key Formula

EROA = \frac{2\pi r^2 \cdot V_a}{V_{max}}

Where:

EROA = Effective Regurgitant Orifice Area

r = Radius of PISA (cm)

Va = Aliasing velocity (cm/s)

Vmax = Peak MR velocity (cm/s) via CW Doppler

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Step-by-Step Technique

1. Optimize Image

Use apical 4-chamber view

Zoom on mitral valve

Adjust color Doppler to visualize clear flow convergence

2. Set Aliasing Velocity

Shift baseline downward

Typical Va = 30–40 cm/s

3. Measure Radius (r)

Measure from orifice to first aliasing boundary

4. Obtain MR Velocity

Use CW Doppler to get Vmax

5. Calculate EROA

Apply formula above

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Regurgitant Volume (RVol)

RVol = EROA \times VTI_{MR}

VTI_MR = Velocity Time Integral of MR jet

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Severity Grading (Guideline-Based)

Severity EROA (cm²) Regurgitant Volume (mL)

Mild < 0.20 < 30

Moderate 0.20–0.39 30–59

Severe ≥ 0.40 ≥ 60

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Advantages

Quantitative and guideline-recommended

Useful in primary MR assessment

More reliable than jet area alone

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Limitations / Pitfalls

Assumes hemispheric geometry (not always true)

Eccentric jets → underestimation

Multiple jets → inaccurate

Sensitive to gain and aliasing settings

Not reliable in irregular rhythms (e.g., AF)

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Clinical Pearls

Best for central MR jets

Always integrate with:

Vena contracta

Pulmonary vein flow

LV size and function

Avoid relying on PISA alone