What does a PISA (Pressure Half-Time Index for Severity of regurgitation or stenosis) value of 0.5 indicate in terms of left ventricular function?

PISA Value of 0.5 in Valvular Regurgitation Assessment

A PISA (Proximal Isovelocity Surface Area) radius of 0.5 cm indicates moderate valvular regurgitation, suggesting significant but not severe regurgitant flow that may affect left ventricular function over time if not monitored appropriately. 1, 2

Understanding PISA Measurement and Its Significance

The PISA method is a quantitative approach used to assess the severity of valvular regurgitation by measuring the radius of the flow convergence zone proximal to the regurgitant orifice. This measurement is then used to calculate:

• Effective Regurgitant Orifice Area (EROA)
• Regurgitant Volume (RVol)
• Regurgitant Fraction (RF)

PISA Radius to Severity Correlation

When interpreting a PISA radius of 0.5 cm:

• For mitral regurgitation:

  • PISA radius <0.5 cm typically indicates mild regurgitation
  • PISA radius of 0.5-0.9 cm suggests moderate regurgitation
  • PISA radius ≥0.9 cm indicates severe regurgitation 2

• For aortic regurgitation:

  • Similar thresholds apply, though with slightly different cutoffs depending on the specific guidelines 1

Impact on Left Ventricular Function

A PISA radius of 0.5 cm has the following implications for left ventricular function:

1. Volume Load: Creates a moderate additional volume load on the left ventricle that may lead to progressive LV dilatation over time 1

2. Compensatory Mechanisms: The LV typically responds with mild to moderate eccentric hypertrophy to handle the increased volume 3

3. Ejection Fraction: Usually preserved in the early to intermediate stages of regurgitation with this degree of severity 3

4. Long-term Effects: Without intervention, chronic moderate regurgitation may eventually lead to LV dysfunction, though at a slower rate than severe regurgitation 1

Quantitative Assessment Using PISA

Using the standard formula with a PISA radius of 0.5 cm:

EROA = 2πr² × (aliasing velocity ÷ peak regurgitant velocity)

With typical settings and a PISA radius of 0.5 cm, this simplifies to approximately: EROA ≈ 0.5²/2 = 0.125 cm² 2

This EROA value falls within the moderate range for both mitral and aortic regurgitation:

• For MR: 0.2-0.39 cm² is considered moderate
• For AR: 0.10-0.29 cm² is considered moderate 1

Clinical Implications and Monitoring

With a PISA radius of 0.5 cm indicating moderate regurgitation:

• Follow-up Echocardiography: Recommended every 6-12 months to monitor for progression of regurgitation and LV dimensions 1

• LV Parameters to Monitor:

  • LV end-diastolic and end-systolic dimensions
  • LV ejection fraction
  • LV volumes (indexed to body surface area) 1

• Symptoms: Patients may be asymptomatic or have mild symptoms during exertion 3

Limitations and Considerations

It's important to recognize several limitations when interpreting a PISA radius of 0.5 cm:

1. Measurement Error: A difference of just 1mm in PISA radius measurement can significantly change the calculated EROA and severity classification 2

2. Geometric Assumptions: The PISA method assumes a round orifice through a flat surface and a hemispheric flow convergence region, which may not always be accurate 2

3. Jet Direction: Eccentric jets may lead to underestimation of severity 1

4. Multiple Jets: If multiple regurgitant jets are present, the PISA method may underestimate total regurgitation 1

5. Integration with Other Parameters: PISA should never be used in isolation but integrated with other echocardiographic parameters for a comprehensive assessment 2

Bottom Line

A PISA radius of 0.5 cm indicates moderate valvular regurgitation with potential long-term implications for left ventricular function. While not immediately concerning for most patients with preserved LV function, it warrants regular monitoring and consideration of the overall clinical context to determine appropriate management strategies.