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Measuring PISA
1. PISA is Proximal Isovelocity Surface Area. It is larger in large volume jets and smaller in small volume jets. It also will change its size depending on the color Doppler scale factor.
2. PISA is just one of many ways to calculate severity of MR.
3. There are four hallmarks of flow in mitral regurgitation: flow convergence that then narrows into an area called the vena contracta (narrowest flow) and then expands into the area of turbulence (what we currently call the size of the jet. We also can see the downstream effects like pulmonary vein flow reversal in systole.
4. The PISA can be seen on this TEE MR jet.
5. And the vena contracta can be seen on this same jet.
6. The four hallmark areas we mentioned before are called: PISA, vena contracta, jet size and pulmonary vend reversal.
7. The area of flow convergence is where we look for PISA. There are many concentric flow velocity shells as flow accelerates into the vena contracta.
8. Calculation of PISA requires us to find one of these shells and then calculate its surface area. Yes, this takes a lot of faith and skill. It is almost always done from an apical view.
9. These are the hallmark flow areas on a diagram of mitral regurgitation.
10. One thing to remember is that PISA (as well as the other hallmark areas) will be larger in large degrees of mitral regurgitation.
11. These are the steps to perform PISA calculations.
12. Every MR jet has a flow convergence area and, therefore, a PISA of the jet.
13. PISA looks at the flow convergence.
14. Keep in mind, flow is always the area x the velocity. We learned this in the continuity equation and in Doppler calculations of cardiac output.
15. But we canít clearly see the orifice, so for PISA we will look prior to the orifice. We will look at one of the isovelocity shells.
16. Here area of the shell x velocity of the shell equals flow. By the continuity equation, this flow should be exactly that of the flow at the regurgitant orifice.
17. So find a velocity shell and move the scale factor to help you identify it.
18. Moving the scale factor down will make the shell bigger and easier to identify. Now you have the shell and you can read the velocity.
19. Since you have the shell, measuring the radius will allow you to calculate the area of the shell or PISA.
20. If you multiply the area x velocity you will get the flow.
21. Note the PISA get larger in this MR jet. The jet at the right is the same as on the left, the only thing changed is the scale factor.
22. Here is a larger depiction of the previous jets.
23. So remember that PISA will get bigger with more flow (bigger jets). It also will get bigger as you shift the scale factor down.
24. The use of the scale factor just helps you identify a suitable isovelocity shell for measurement. Then you can use it to calculate flow.
25. The biggest limitation of PISA is the incorrect identification of the proximal flow convergence area.
26. Here is an area where the flow convergence is not symmetric.
27. This is an example of a perforated mitral leaflet from the TEE approach (left). Note the asymmetric flow convergence area. This is a limitation of PISA.
28. So we worry about non-optimal flow convergence and changes in the PISA over time (the cardiac cycle).
29. Note the changes in size over the cardiac cycle.
30. So PISA has limitations. Look in your favorite text for the ranges of values but keep in mind, big is big and small is small.

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