PISA Method for Aortic Regurgitation (AR)

 

PISA Method for Aortic Regurgitation (AR)

Concept

PISA (Proximal Isovelocity Surface Area) is based on the principle that blood accelerates toward a regurgitant orifice forming hemispheric shells of equal velocity. By measuring these, we can quantify regurgitant flow.

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Key Formula

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

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Parameters

r = PISA radius (cm)

V_alias = aliasing velocity (cm/s)

Vmax = peak AR velocity by CW Doppler (cm/s)

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Regurgitant Volume

RVol = EROA \times VTI_{AR}

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Step-by-Step Technique

1. Use apical 5-chamber or long-axis view

2. Apply color Doppler over aortic valve

3. Lower Nyquist limit (~30–40 cm/s)

4. Zoom on LVOT/aortic valve

5. Identify flow convergence (hemisphere)

6. Measure radius (r) from orifice to aliasing line

7. Record Vmax and VTI using CW Doppler

8. Apply formulas

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Severity Cutoffs (Guideline-Based)

Severity EROA (cm²) Regurgitant Volume (mL)

Mild <0.10 <30

Moderate 0.10–0.29 30–59

Severe ≥0.30 ≥60

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Important Limitations

Assumes hemispheric geometry → often distorted in AR

Difficult in eccentric jets

Less accurate than in MR

Errors with improper aliasing velocity

LVOT and valve anatomy may distort measurement

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Clinical Pearl

PISA in AR is supportive, not standalone. Always integrate with:

Vena contracta width

Pressure half-time

Diastolic flow reversal in aorta

LV size and function

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One-Line Summary

PISA in AR estimates EROA and regurgitant volume using flow convergence, but due to geometric limitations, it should always be integrated with multiparametric assessment.