Pisa Calculator - Echo MR and MS Severity

A PISA calculator turns five Doppler echo measurements, the PISA radius, the aliasing velocity, the peak mitral velocity, the leaflet angle, and the velocity time integral, into the five numbers a cardiology reader needs at the bedside: the hemisphere area itself, the volume flow rate, the effective regurgitant orifice area, the regurgitant volume per beat, and the mitral valve area. The result panel pairs the EROA and RVol with the American Society of Echocardiography mitral regurgitation severity bands, and the MVA with the mitral stenosis severity bands, so the same form handles the two most common valvular questions asked of a PISA study.

• • Grade chronic primary mitral regurgitation: Drop in the PISA radius, aliasing velocity, Vmax, and VTI from a transthoracic Doppler and read the EROA, RVol, and MR severity band.
• • Estimate mitral valve area for rheumatic mitral stenosis: Use the alpha angle branch to convert the hemisphere into a true flow area and read the MVA and MS severity band together.
• • Triage severe findings between echo and cath: Read the EROA against the ASE severe band (at or above 0.40 cm^2) and the RVol against the severe band (at or above 60 mL per beat) to escalate to a cardiology referral.

PISA stands for proximal isovelocity surface area. The method treats the proximal flow convergence zone on the atrial side of the regurgitant orifice as nested hemispheres that carry the same flow, and reads the largest visible hemisphere as a single radius r. The hemisphere area is 2 pi r squared, and the rest of the calculation chains that area to the volume flow rate, the EROA, the RVol, and the MVA.

When the PISA study is the mitral valve and the next question is the aortic valve, the Aortic Valve Area Calculator handles the continuity equation on the same Doppler workflow.

The form works in three short chains. The PISA branch computes the hemisphere area and the volume flow rate from the radius and the aliasing velocity. The mitral regurgitation branch divides the flow rate by Vmax to get the EROA and multiplies the EROA by the VTI to get the RVol. The mitral stenosis branch scales the hemisphere by alpha divided by 180 and divides by Vmax to get the MVA.

• r: PISA radius from the vena contracta to the furthest edge of the hemisphere, in cm.
• Vr: Aliasing velocity at the radius r, set by the color Doppler Nyquist limit, in cm per second.
• Vmax: Peak mitral velocity from the continuous-wave Doppler tracing, in cm per second.
• alpha: Angle between the two mitral leaflets on the atrial side, in degrees, used for the stenosis branch.
• VTI: Velocity time integral of the mitral regurgitant jet, in cm. Set to zero when only the EROA is needed.

EROA is reported in cm squared inside the form, but the ASE severity table uses mm squared. The calculator keeps the native cm squared value in the result panel so the reader can compare it to planimetry and to the indexed MVA.

According to American Society of Echocardiography Valve Disease Resource Library, the proximal isovelocity surface area method treats the flow convergence zone as a hemisphere of radius r and combines the hemisphere area with the continuous-wave Doppler peak velocity and the velocity time integral to grade mitral regurgitation severity.

As published by European Society of Cardiology Valvular Heart Disease Guidelines, the PISA-derived EROA and RVol are the preferred quantitative Doppler criteria for grading chronic primary mitral regurgitation, and a mitral valve area below 1.0 cm squared marks severe rheumatic mitral stenosis.

When the Vmax is being read off a continuous-wave Doppler trace at a high heart rate, the ECG Heart Rate Calculator confirms the rate from the ECG strip so the PISA study and the rhythm read line up.

Four concepts drive the result. Naming them keeps the PISA calculator from being read as a single lab number, which it is not.

The same hemisphere area answers two different questions depending on which branch the reader follows. The regurgitation branch reads the hemisphere as a flow, and the stenosis branch reads it as a constricted disc.

Chronic primary mitral regurgitation shares cardiovascular risk factors with atherosclerotic disease, and the LDL Calculator converts total cholesterol, HDL, and triglycerides into an LDL estimate to put on the same clinic note as the PISA severity band.

The form works from a small set of Doppler measurements. Each input should be set to a value that reflects the measurement as it was taken, not an idealised version.

1. 1 Measure the PISA radius r on the color Doppler image: Set the color Nyquist limit so the aliasing velocity Vr is between 10 and 40 cm per second, then measure the radius from the vena contracta to the furthest edge of the hemisphere in mid-systole.
2. 2 Read the aliasing velocity Vr from the color bar: The Vr is the velocity at the aliasing boundary where the color flips, in cm per second.
3. 3 Trace the continuous-wave Doppler for Vmax and VTI: From the apical view, place the continuous-wave Doppler cursor through the mitral valve and trace the outer edge of the envelope for Vmax and VTI.
4. 4 Measure the leaflet angle alpha in the parasternal long axis: For stenosis, freeze the frame at maximal diastolic opening and measure the angle between the two leaflet tips on the atrial side.
5. 5 Read the result panel: Look at PISA, VFR, EROA, RVol, MVA, and the two severity bands together, and bring the result to the cardiology review.

A reader with r 0.5 cm, Vr 10 cm per second, Vmax 30 cm per second, alpha 25 degrees, and VTI 10 cm can read PISA 1.57 cm squared, VFR 15.71 mL per second, EROA 0.52 cm squared, RVol 5.24 mL per beat, MVA 0.07 cm squared, and the two severity bands.

When the MR severity band is in front of the reader, the Arterial Age Calculator returns a vascular age that pairs with the PISA result on the same clinic note.

Calculating PISA, EROA, RVol, MVA, and VFR from a small set of Doppler measurements has several practical benefits over running the math by hand.

• • Five outputs from one form: A single form returns the PISA hemisphere area, the volume flow rate, the EROA, the RVol, and the MVA, so the reader does not have to recompute the hemisphere area by hand for each branch.
• • Both MR and MS severity bands: The result panel pairs the EROA and RVol with the ASE mitral regurgitation severity bands, and the MVA with the mitral stenosis severity bands.
• • Source-traced formula chain: The PISA, EROA, RVol, and MVA branches are all shown as a single formula chain, so a sonographer can show a fellow where each output comes from.
• • Real-time Doppler adjustments: Each input updates the result panel as soon as it changes, which makes it easy to spot a noisy VTI or a mis-set color Nyquist limit.

The form is a planning tool, not a clinical decision. The final call sits with the cardiology or cardiothoracic surgery team alongside symptoms, valve morphology, and exercise testing.

Once the mitral regurgitation grade is in hand, the next cardiovascular risk question is usually the cholesterol ratio, and the Cholesterol Ratio Calculator returns the total cholesterol to HDL, LDL to HDL, and triglyceride to HDL ratios on the same screen.

Several factors shape the result. The most important ones sit inside the entered form, and a small set of caveats belong outside the form.

• • The PISA calculator assumes a hemispheric flow convergence. In some patients the flow convergence is hemi-elliptic, and 3D echo or a hemi-elliptic correction can give a more accurate EROA and MVA.
• • The result is a planning estimate, not a diagnosis. The final clinical decision sits with the cardiology or cardiothoracic surgery team alongside symptoms and exercise testing.

The ASE severity table for mitral regurgitation pairs the EROA in mm squared with the RVol in mL per beat, so a value above the severe band is reassuring only when both numbers agree.

According to ACC/AHA 2020 Valvular Heart Disease Guideline, severe mitral stenosis is a mitral valve area below 1.0 cm squared and severe chronic primary mitral regurgitation uses an EROA at or above 0.40 cm squared paired with a regurgitant volume at or above 60 mL per beat.