The PISA calculator is a measuring tool to evaluate mitral valve regurgitant volume, mitral regurgitation level, and the regurgitant orifice and volume, following the Doppler measurements. By measuring all these factors, this calculator helps you to know about mitral stenosis, volume flow rate, and mitral valve area calculation. The mitral valve is an important anatomic reference point between the upper and lower left heart chambers to control blood flow. Any disturbance in the valve area can affect the normal blood flow leading to multiple heart-related disorders.
This article explains the clear concepts related to the PISA calculator to evaluate the measurements associated with the mitral valve. In addition, it provides an easy understanding of mitral valve-related disorders to enhance your knowledge.
Is it possible to calculate PISA on an echocardiogram?
PISA explains the full form of proximal isovelocity surface area. It is a manual method for echocardiographic evaluation of mitral valve regurgitation, valve area, and mitral stenosis severity. With this method, we can calculate the area for the hemisphere of the circular orifice of the mitral valve.
There is a well-known venturi effect, also known as the open door effect. It explains the acceleration of fluid or air when it crosses a narrower orifice or opening. The same effect is applicable to the mitral valve orifice. The accelerating speed of the blood flow is directly proportional to the speed it achieves while crossing the mitral valve. It indicates that the narrower the orifice, the higher the speed. Unfortunately, this does not exactly happen in the case of living things. Fluids tend to increase their speed before crossing the orifice. For this reason, it is better to measure to assess the area for a hemisphere.
For this, Doppler echocardiography and a PISA calculator are mandatory to evaluate the area.
How to measure PISA?
PISA should be measured at its peak point along a single plane. It is better to visualize the line when it is directly within the range of your probe’s beam.
- Sometimes, it is quite straightforward to measure and visualize PISA. It is common among patients with severe mitral stenosis. Consider maximizing your scale for better evaluation.
- Save more than one plane to properly visualize and look for the greatest visible PISA.
- Calculate the PISA radius from the vena contracta (a point of the orifice indicating the maximum fluid speed with the smallest diameter of the fluid stream) up to the farthest edge of the PISA.
- Consider this obtained radius to perform further calculations, including PISA mitral regurgitation or valve area.
How can we use this PISA calculator?
There is nothing to get confused about in the complex calculations of the PISA calculator. Here is a way to explain the details of the PISA calculator for your ease. The PISA method follows the continuity equation to evaluate the area of effective regurgitant orifice area based on different other values.
Volume flow rate = 2 × π × r² (radial distance) × VR (aliasing velocity)
Effective regurgitant orifice ERO (mm²) = VFR / Vmax (peak mitral stenosis velocity)
PISA (cm²) = 2πr²
The mitral regurgitant volume is further evaluated by the following equation formula.
Regurgitant volume RVol (mL/beat) = ERO × velocity time integral (VTI)
For the evaluation of the mitral valve area to assess the stenosis, we use the following equation.
Mitral valve area = [2πr² × Vr × (alpha angle / 180)] / Vmax
The alpha angle indicates the angle between two mitral leaflets on the atrial aspect.
How to interpret the values of the PISA calculator?
This article not only covers the usage details of the PISA calculator but also provides the details underlying this PISA calculator. These are the values indicating the level of mitral regurgitation on the echocardiogram.
|Mitral regurgitation level:||Effective regurgitant orifice (mm²):||Regurgitant volume (mL/beat):|
|Mild:||Lesser than 20||Lesser than 30|
|Mild to moderate:||20 to 29||30 to 44|
|Moderate to severe:||30 to 39||45 to 59|
|Severe:||≥ 40||≥ 60|
Mitral valve area:
|Level:||Mitral valve area (cm²):|
|Normal:||4.0 to 5.0|
|Mild:||Greater than 1.5|
|Moderate:||Ranging between 1.0 to 1.5|
|Severe:||Lesser than 1.0|
How to use this PISA calculator in clinical practice?
Let us take an example for a better understanding of this PISA calculator. For example, we obtained the following values from the Doppler ultrasound of a patient. Let’s suppose these are the obtained values.
- Peak mitral velocity or Vmax = 40 cm/second
- Radial distance = 0.7 cm
- Aliasing velocity at r or Vr = 15 cm/second
- Alpha angle = 27 degrees
- Velocity time integral = 12 cm
- For the mitral valve area, we will use the values of Vmax, r, Vr, and alpha angle. Following the value of the mitral valve area, the PISA calculator helps to assess the level of mitral valve stenosis. The details of this patient indicate severe mitral stenosis.
- To know about the regurgitation level, we will use values of r, Vr, and Vmax to assess the effective regurgitant orifice. In addition, if you add the velocity time integral, this calculator will also provide you with the regurgitant volume. In this patient’s case, the effective regurgitant orifice indicates the severe and regurgitant volume of severe mitral regurgitation.
- For PISA, you only need to know about the r value. For this patient, the value of PISA is 3.079.
The PISA calculator explains the abbreviation of the proximal isovelocity surface area calculator. It follows the hemodynamic principle to evaluate the degree of mitral valve insufficiency. This calculator provides multiple ranges of values related to the mitral valve. In addition, it also helps to evaluate the regurgitation level. Moreover, there are several associated factors that can describe the severity of mitral stenosis, following the mitral valve area. This article is all about the mitral valve regurgitation calculation. Give it a read to avoid complex calculations for mitral valve regurgitant volume and surface area. Just out the specific values and get your desired results.
Frequently asked questions (FAQs)
On which method, the PISA calculator relies on?
The PISA calculator relies on the principle of flow convergence that describes the area of an orifice to which blood flows. This calculator also provides multiple other values related to mitral regurgitation.
What are the findings associated with the mitral valve area of 0.9?
A mitral valve area of 0.9 indicates a very decreased area of the valve. It indicates a medical condition known as severe mitral valve stenosis. In the article, we mentioned the criteria of the mitral valve to assess the severity level of mitral stenosis.