A PISA radius greater than which value indicates severe mitral regurgitation?

• A. >9 mm
• B. <5 mm
• C. 7-8 mm
• D. 3-4 mm

Answer: (A)

The key idea is the PISA method: as the flow convergence region in front of the mitral valve becomes larger (measured as the radius of the hemispheric isovelocity surface), the amount of regurgitant flow increases. Measuring the radius at a preset aliasing velocity lets us estimate how much blood is leaking backward. A PISA radius greater than about 9 mm (0.9 cm) indicates a high regurgitant flow, which corresponds to severe mitral regurgitation. In standard practice, smaller radii are associated with milder MR (roughly <5 mm for mild, ~7–8 mm for moderate), while radii exceeding 9 mm push into the severe range. Remember this method assumes a single, central jet and a hemispheric flow convergence; multiple jets or non-hemispheric flow can affect accuracy.