2. Regurgitant volumes can be estimated by 2Regurgitant volumes can be estimated by 2
methodsmethods
Volumetric methodVolumetric method
PISA methodPISA method
As we knowAs we know
Flow rate = CSA x VelocityFlow rate = CSA x Velocity
Volume = CSA x TVIVolume = CSA x TVI
3. If regurgitant orifice area is known thenIf regurgitant orifice area is known then
reguritant volume can be estimated as thereguritant volume can be estimated as the
product of effective regurgitant orifice areaproduct of effective regurgitant orifice area
(ERO) and regurgitant TVI(ERO) and regurgitant TVI
To estimate ERO, Proximal isovelocity surfaceTo estimate ERO, Proximal isovelocity surface
area is usedarea is used
RV = ERO x Regurgitant TVIRV = ERO x Regurgitant TVI
4. As blood flow converges towards the regurgitantAs blood flow converges towards the regurgitant
orifice, blood flow velocity increases withorifice, blood flow velocity increases with
formation of multiple shells of isovelocity offormation of multiple shells of isovelocity of
hemispheric shapehemispheric shape
Remember that velocity of the shell closest toRemember that velocity of the shell closest to
the regurgitant orifice is highest and vice versathe regurgitant orifice is highest and vice versa
The flow rate at the surface of a hemisphericThe flow rate at the surface of a hemispheric
shell with the same flow velocity is consideredshell with the same flow velocity is considered
equal to the flow rate across the regurgitantequal to the flow rate across the regurgitant
orifice according to the law of conservation oforifice according to the law of conservation of
flow which states thatflow which states that
““What comes in must go out”What comes in must go out”
5. By adjusting the Nyquist limit of the color flow map, theBy adjusting the Nyquist limit of the color flow map, the
flow velocity of a hemispheric surface proximal to theflow velocity of a hemispheric surface proximal to the
regurgitant orifice can be determinedregurgitant orifice can be determined
For e.g. in MR the regurgitant flow travels away from theFor e.g. in MR the regurgitant flow travels away from the
position of the apical transducer ans so the bloodposition of the apical transducer ans so the blood
converging towards the mitral regurgitant orifice in theconverging towards the mitral regurgitant orifice in the
LV is color coded blue until the velocity reaches theLV is color coded blue until the velocity reaches the
negative aliasing velocity of the selected color flow map,negative aliasing velocity of the selected color flow map,
at which time the flow will change color to light orange-at which time the flow will change color to light orange-
redred
If the negative aliasing velocity of the color map isIf the negative aliasing velocity of the color map is
reduced further, the trasition from blue to orange-red willreduced further, the trasition from blue to orange-red will
occur farther from the regurgitant orifice providing aoccur farther from the regurgitant orifice providing a
larger hemispheric shell radiuslarger hemispheric shell radius
6. After a hemisphere with blood flow of isovelocityAfter a hemisphere with blood flow of isovelocity
is identified the flow rate through thisis identified the flow rate through this
hemispheric shell is determined byhemispheric shell is determined by
Flow rate = CSA x VelocityFlow rate = CSA x Velocity
Area of hemispheric shell = 2Area of hemispheric shell = 2ππr², where pie=3.14r², where pie=3.14
Flow rate = 6.28 x r² x Aliasing velocity (from color map)Flow rate = 6.28 x r² x Aliasing velocity (from color map)
7. As we have already discussed the flow rate atAs we have already discussed the flow rate at
the surface of a hemispheric shell with the samethe surface of a hemispheric shell with the same
flow velocity is considered equal to the flow rateflow velocity is considered equal to the flow rate
across the regurgitant orifice according to theacross the regurgitant orifice according to the
law of conservation of flowlaw of conservation of flow
Therefore, this flow across PISA is equal to flowTherefore, this flow across PISA is equal to flow
rate across EROrate across ERO
Flow rate = ERO x regurgitant velocityFlow rate = ERO x regurgitant velocity
ERO = flow rate / peak MR velocityERO = flow rate / peak MR velocity
ERO = 6.28 x r² x Aliasing velocity / MR velocityERO = 6.28 x r² x Aliasing velocity / MR velocity
8. Regurgitant Volume = ERO x MR TVIRegurgitant Volume = ERO x MR TVI
Substituting value of ERO we getSubstituting value of ERO we get
Regurg Vol = 6.28 x r² xRegurg Vol = 6.28 x r² x Aliasing velocityAliasing velocity x MRTVIx MRTVI
MR velocityMR velocity
9. The concept of PISA can also be applied toThe concept of PISA can also be applied to
calculate the area of stenotic surfaces and hascalculate the area of stenotic surfaces and has
been validated for MV area in patients with mitralbeen validated for MV area in patients with mitral
stenosisstenosis
10. CaveatsCaveats
Proximal to a stenotic mitral orifice, PISA mayProximal to a stenotic mitral orifice, PISA may
not be a complete hemisphere but a portion ofnot be a complete hemisphere but a portion of
hemisphere because of mitral leaflets geometryhemisphere because of mitral leaflets geometry
on the atrial sideon the atrial side
In such cases an angle correction factor isIn such cases an angle correction factor is
appliedapplied
MVA = 6.28 x r² xMVA = 6.28 x r² x Aliasing velocityAliasing velocity xx alphaalpha°°
Peak MS velocity 180Peak MS velocity 180°°
Where alpha is the angle between two mitral leaflets on the atrial sideWhere alpha is the angle between two mitral leaflets on the atrial side
11. Sometimes it is difficult to know in which direction theSometimes it is difficult to know in which direction the
baseline should be shifted for optimal PISAbaseline should be shifted for optimal PISA
For this rule of the thumb is to shift the baseline inFor this rule of the thumb is to shift the baseline in
the direction of the flow jet of interestthe direction of the flow jet of interest
PISA radius needs to be measured at the same time asPISA radius needs to be measured at the same time as
the peak velocity of the jetthe peak velocity of the jet
Color M-mode can help in measuring the radiusColor M-mode can help in measuring the radius
reliably at the correct timereliably at the correct time
12. Measuring PISAMeasuring PISA
PISA is Proximal Isovelocity Surface AreaPISA is Proximal Isovelocity Surface Area
It is larger in large volume jets and smaller inIt is larger in large volume jets and smaller in
small volume jetssmall volume jets
It also will change its size depending on theIt also will change its size depending on the
color Doppler scale factorcolor Doppler scale factor
13. PISA is just one of many ways to calculatePISA is just one of many ways to calculate
severity of MRseverity of MR
14. There are four hallmarks of flow in mitralfour hallmarks of flow in mitral
regurgitation:regurgitation:
Flow convergenceFlow convergence that then narrows into anthat then narrows into an
area ofarea of accelarated flowaccelarated flow (narrowest area of(narrowest area of
flow) and then expands into the area offlow) and then expands into the area of
turbulence (what we currently call theturbulence (what we currently call the size ofsize of
the jetthe jet))
We also can see the downstream effects likeWe also can see the downstream effects like
pulmonary vein flow reversalpulmonary vein flow reversal in systolein systole
16. So the hallmark flow areas on a diagram ofSo the hallmark flow areas on a diagram of
mitral regurgitationmitral regurgitation
17. The PISA can be seen on this TEE MR jetThe PISA can be seen on this TEE MR jet
18. And the vena contracta can be seen on thisAnd the vena contracta can be seen on this
same jetsame jet
19. The area of flow convergence is where we lookThe area of flow convergence is where we look
for PISAfor PISA
There are many concentric flow velocity shellsThere are many concentric flow velocity shells
as flow accelerates into the vena contractaas flow accelerates into the vena contracta
20. Calculation of PISA requires us to find one ofCalculation of PISA requires us to find one of
these shells and then calculate its surface areathese shells and then calculate its surface area
This takes a lot of faith and skillThis takes a lot of faith and skill
It is almost always done from an apical viewIt is almost always done from an apical view
21. One thing to remember is that PISA (as well asOne thing to remember is that PISA (as well as
the other hallmark areas) will be larger in largethe other hallmark areas) will be larger in large
degrees of mitral regurgitationdegrees of mitral regurgitation
23. Every MR jet has a flow convergence area and,Every MR jet has a flow convergence area and,
therefore, a PISA of the jettherefore, a PISA of the jet
24. PISA looks at the flow convergencePISA looks at the flow convergence
25. Keep in mind, flow is always the area x theKeep in mind, flow is always the area x the
velocityvelocity
We already know this from the continuityWe already know this from the continuity
equation and in Doppler calculations of cardiacequation and in Doppler calculations of cardiac
outputoutput
26. But we can’t clearly see the orifice, so for PISABut we can’t clearly see the orifice, so for PISA
we will look prior to the orificewe will look prior to the orifice
We will look at one of the isovelocity shellsWe will look at one of the isovelocity shells
27. Here area of the shell x velocity of the shellHere area of the shell x velocity of the shell
equals flowequals flow
By the continuity equation, this flow should beBy the continuity equation, this flow should be
exactly that of the flow at the regurgitant orificeexactly that of the flow at the regurgitant orifice
28. So find a velocity shell and move the scale factorSo find a velocity shell and move the scale factor
to help you identify itto help you identify it
29. Meaning of scale factorMeaning of scale factor
The use of the scale factor just helps us identifyThe use of the scale factor just helps us identify
a suitable isovelocity shell for measurementa suitable isovelocity shell for measurement
Then we can use it to calculate flowThen we can use it to calculate flow
30. Note the PISA get larger in this MR jet. The jet atNote the PISA get larger in this MR jet. The jet at
the right is the same as on the left, the only thingthe right is the same as on the left, the only thing
changed is the scale factorchanged is the scale factor
31. Here is a larger depiction of the previous jetsHere is a larger depiction of the previous jets
32. Moving the scale factor down will make the shellMoving the scale factor down will make the shell
bigger and easier to identify.bigger and easier to identify.
So, now we have the shell and can read theSo, now we have the shell and can read the
velocityvelocity
33. Since we have the shell, measuring the radiusSince we have the shell, measuring the radius
will allow you to calculate the area of the shell orwill allow you to calculate the area of the shell or
PISAPISA
34. If we multiply the area x velocity we will get theIf we multiply the area x velocity we will get the
flowflow
36. LimitationsLimitations
The biggest limitation of PISA is the incorrectThe biggest limitation of PISA is the incorrect
identification of the proximal flow convergenceidentification of the proximal flow convergence
areaarea
37. Here is an example of an area where the flowHere is an example of an area where the flow
convergence is not symmetricconvergence is not symmetric
38. This is an example of a perforated mitral leafletThis is an example of a perforated mitral leaflet
from the TEE approach (left)from the TEE approach (left)
Note the asymmetric flow convergence areaNote the asymmetric flow convergence area
This is a limitation of PISAThis is a limitation of PISA
39. So we worry about non-optimal flowSo we worry about non-optimal flow
convergence and changes in the PISA over timeconvergence and changes in the PISA over time
(the cardiac cycle)(the cardiac cycle)
40. Note the changes in size over the cardiac cycleNote the changes in size over the cardiac cycle
41. So PISA has limitationsSo PISA has limitations
Different textbooks have given the ranges ofDifferent textbooks have given the ranges of
values but keep in mind, big is big and small isvalues but keep in mind, big is big and small is
smallsmall