How this instrument works
The proximal isovelocity surface area (PISA) method estimates how much blood is leaking backward through a regurgitant heart valve by measuring the flow converging toward it. As blood approaches a narrow orifice, color Doppler shows it accelerating through a series of roughly hemispherical shells; picking the shell where velocity equals a known aliasing velocity and measuring its radius gives a volume flow rate through the continuity equation, which then converts into the orifice's effective area and the regurgitant volume per heartbeat.
This is the American Society of Echocardiography's standard PISA workflow for grading native valve regurgitation, set out in Zoghbi and colleagues' 2003 recommendations and reaffirmed in the 2017 update. The same four numbers — PISA radius, aliasing velocity, peak regurgitant jet velocity, and the jet's velocity time integral — feed volume flow rate, effective regurgitant orifice area (EROA), regurgitant volume, and a four-tier severity grade running mild, moderate, moderately severe, and severe, using the cutoffs that guideline defines.
This is a clinical reference calculator, not a self-assessment tool. Every input here — PISA radius, aliasing velocity, peak jet velocity, velocity time integral — comes from a real transthoracic or transesophageal echocardiogram, measured and interpreted by a trained sonographer or cardiologist using dedicated ultrasound equipment. There is no way for a patient to obtain any of these four numbers without that professional study already having taken place; this instrument performs the standardized arithmetic a reader applies after the imaging is done, not a diagnostic test anyone can run on themselves.
- Enter PISA radius (r) — the color-Doppler flow-convergence radius measured at the moment velocity equals the aliasing limit, in cm.
- Enter Aliasing velocity (Va) — the Nyquist limit shown on the color-flow scale at the instant r was measured, in cm/s.
- Enter Peak MR jet velocity (Vmax) — the maximum regurgitant jet velocity from continuous-wave Doppler, in cm/s.
- Enter MR jet velocity time integral (VTI) — traced from the same continuous-wave Doppler envelope, in cm.
- Read Volume flow rate, Effective regurgitant orifice area and Regurgitant volume, plus the ASE severity grade they produce.
Worked example — r 0.9 cm, Va 40 cm/s, Vmax 500 cm/s, VTI 150 cm
With a PISA radius of 0.9 cm, aliasing velocity 40 cm/s, peak MR jet velocity 500 cm/s (5 m/s), and VTI 150 cm: volume flow rate = 2π × 0.9² × 40 = 203.58 ml/s. Dividing by peak velocity gives EROA = 203.58 / 500 ≈ 0.4072 cm², at or above the ASE's 0.40 cm² severe cutoff, so this instrument reports severity grade 4. Regurgitant volume = EROA × VTI ≈ 61.07 ml per beat (using the full-precision EROA behind that rounded 0.4072 cm²).
A smaller flow convergence tells a different story. At r = 0.5 cm, Va = 30 cm/s, Vmax = 450 cm/s and VTI = 80 cm: volume flow rate = 2π × 0.5² × 30 = 47.12 ml/s, EROA = 47.12 / 450 = 0.1047 cm² — under the 0.20 cm² threshold, graded mild — with a regurgitant volume of just 8.38 ml per beat.
Questions
Can I use this calculator to diagnose my own heart murmur?
No. Every input this calculator needs — PISA radius, aliasing velocity, peak jet velocity, velocity time integral — can only be measured from a real echocardiogram performed and read by a trained sonographer or cardiologist. There is no way to obtain these numbers at home or from symptoms alone. This tool automates the arithmetic step that follows a professional echo study; it is not a substitute for one, and it cannot tell you whether you have a murmur or a leaking valve in the first place.
What do the severity grades mild, moderate, moderately severe and severe mean?
They're the ASE's standard EROA cutoffs for native regurgitation: under 0.20 cm² is mild, 0.20 to 0.29 cm² is moderate, 0.30 to 0.39 cm² is moderately severe, and 0.40 cm² or higher is severe. These bands come from Zoghbi and colleagues' 2003 recommendations, reaffirmed in the 2017 ASE guideline update, and are used alongside other echocardiographic findings — not in isolation — when a cardiologist grades regurgitation severity.
Is EROA the same thing as regurgitant volume?
No, though they're related. EROA describes the effective size of the leaking orifice itself, in cm² — a measure of the defect. Regurgitant volume describes how much blood actually flows backward through that orifice over one heartbeat, in ml, calculated by multiplying EROA by the jet's velocity time integral. A small orifice with a long, high-velocity jet can still move a meaningful regurgitant volume.
Why does the aliasing velocity matter so much to the result?
Aliasing velocity sets which isovelocity shell the PISA radius is measured on, and the volume flow rate formula uses that velocity directly, multiplied by the radius squared. Choosing too high or too low an aliasing velocity on the ultrasound machine shifts where the shell forms and how easy it is to measure its radius accurately, which is why sonographers adjust the color-scale Nyquist limit deliberately when acquiring these images rather than using a fixed default.
Does this replace 3D echocardiography or cardiac MRI for quantifying regurgitation?
No — PISA is a widely used 2D Doppler method, but it rests on assumptions (a roughly hemispherical flow-convergence shell, a single dominant regurgitant jet) that don't always hold, particularly in functional or eccentric-jet mitral regurgitation. Current ASE guidance treats PISA as one tool among several, and more complex cases are often cross-checked with 3D echocardiography or cardiac MRI, which this calculator doesn't attempt to model.
What if my echo study's radius or velocity measurements are technically difficult to obtain?
The formula will still compute an answer from whatever numbers are entered, but a technically difficult acquisition — a poor imaging window, an irregular or eccentric jet, an unclear aliasing boundary — can make the underlying measurements themselves unreliable before they ever reach this calculator. That judgment call belongs to the sonographer or cardiologist reading the study, not to the arithmetic downstream of it.
References
- Zoghbi et al. 2003, J Am Soc Echocardiogr — PISA/EROA recommendations (PubMed)
- Zoghbi et al. 2017, J Am Soc Echocardiogr — updated ASE regurgitation guideline (PubMed)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.