PISA Evaluation of MR

PISA Evaluation of
Mitral Regurgitation
Raymond Graber, MD
Cardiac Anesthesia Group
University Hospitals Case Medical Center
4/07/2011
Introduction
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Evaluation of MR.
What is PISA?
Physiologic basis
Issues
How to do it with GE Vivid 7.
Zoghbi WA, et al. Recommendations for Evaluation of the Severity of Native Valvular Regurgitation with
Two-dimensional and Doppler Echocardiography. J Am Soc Echocardiogr 2003;16:777-802.
In the OR, typical methods for MR evaluation include qualitative
measures such as color jet area, chamber size, and pulmonary vein flow.
Quantitative measures include vena contracta and measures of EROA
and regurgitant volume.
Regurgitant Color
Doppler Flow
Pattern:
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Distal jet.
Vena contracta
Proximal flow
convergence
Jet Area Issues
Evaluating color jet area would seem to be an easy thing to do, but
there are multiple caveats:
 Assumes that regurgitant velocities correlates with regurgitant
volumes.
 Is one point in time, whereas volume includes duration of flow.
 Behavior of jet depends on receiving chamber – can be
constrained by side of atrium
 Jets can course outside of ultrasound plane.
 Depend on machine settings.
 Depends on driving pressure across the mitral valve.
Phenylephrine used to elevate BPsys by 40-50
mm Hg in group A.
Gain settings changed.
Fehske W et al: Am J Cardiol 73:268-274, 1994
Note the overlap between groups!
What is PISA?
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PISA = Proximal Isovelocity Surface Area
A concept that can be used to help determine
size of a regurgitant or stenotic orifice.
Based on flow dynamics, use of aliasing and
continuity principle.
Flow Dynamics 1
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When fluid is forced from a chamber thru an
orifice, the fluid accelerates towards the orifice,
and velocity is greatest at the narrowest point of
the orifice.
Flow Dynamics 2
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Conceptually, this results in a series of
concentric hemispheres of increasing velocity as
the orifice is approached. These are the
proximal isovelocity hemispheric shells that we
will calculate the surface area of.
Use of Aliasing
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With color Doppler, as
flow accelerates towards
orifice – at some point,
velocity may exceed the
aliasing velocity, and
color will reverse from
red to blue. At this
hemisphere, the velocity
is thus known (it equals
the aliasing velocity).
Continuity Principle
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Because of the conservation of mass principle, flow
rate must remain constant along the length of a conduit
(assuming the absence of any leaks or additional input)
A1 x V1 = A2 x V2
Applying this to MR:
Regurgitant Orifice Flow = Flow at hemisphere
of color change
EROA x Vorifice = Ahemisphere Vhemisphere
Vorifice =Vmax (by CWD)
Ahemisphere = 2πr2
Vhemisphere = VAliasing
EROA x Vmax = 2 πr2 x VAliasing
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The end result:
EROA = 2 πr2 (VAliasing / Vmax)
RVmr = EROA x TVImr
Assumptions:
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Assumes accurate Doppler measurement of regurgitant
velocity.
Assumes regurgitant orifice is circular.
Assumes that the orifice is on a planar surface, and that
the incoming flow forms a complete hemisphere.
Assumes single orifice.
Depends on accurate measurement of radius.
Assumes that regurgitant orifice is constant in size.
Can we measure regurgitant velocity
accurately with Doppler?
Central jet: good
CWD curve.
Eccentric jet:
suboptimal
CWD curve.
Are Regurgitant Orifices Circular?
This 3D
TEE shows
a regurgitant
orifice that is
elongated.
Other mathematical
models being
developed for PISA in
non-hemispherical
orifices.
Rifkin and Sharma. Alternative Isovelocity Surface Model. J A
C C : Cardiovascular Imaging 2010
Is the orifice on a planar surface?
Eccentric jets frequently don’t have a planar surface.
A correction factor (a/180) can be used.
(Multiply this times the calculated EROA and RV)
Is There A Single Orifice?
Frequently not!
Getting an Accurate
Measurement of Radius:
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Adjusting the aliasing
velocity by shifting the
color Doppler baseline
towards the direction
of flow increases the
measured radius and
improves accuracy.
Is the Regurgitant Orifice
Constant In Size?
Orifices can change
in size over time,
especially with
prolapse. It is
recommended to use
the PISA radius that
corresponds to the
time of peak
regurgitant velocity.
(J Am Coll Cardiol Img 2010; 3:235– 43)
How good are these measurements? Can we agree upon them?
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In the ideal situation
clinicians would look at a
measure, and all would agree
that the MR was severe, or
agree that it was not. Yet in
this study, was not the case.
For example, looking at Jet
size in patient 1, 39% rated it
as severe, and 61% rated it as
not severe!
Cardiologist Agreement
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The authors defined
“substantial agreement” as
>80% of cardiologists were in
agreement with a finding for a
specific patient.
In what % of images was there
substantial agreement? :
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Jet Area: 44%
Vena Contracta: 44%
EROA: 38%
Reasons for Variability of Assessments
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> 30% variation of PISA radius during the
course of the MR jet: 44%
> 30% variation of VC width during the
course of the MR jet : 44%
Effective MR orifice identifiable: 44%
Eccentric were much harder to evaluate
quantitativly then central jets
Their Conclusions:
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The VC and PISA measurements for distinction of
severe versus non-severe MR are only modestly reliable
and associated with suboptimal interobserver
agreement.
The presence of an identifiable effective regurgitant
orifice improves reproducibility of VC and a central
regurgitant jet predicts substantial agreement among
multiple observers of PISA assessment.
Example: PISA Step By STEP
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Use MELAX view, obtain image of MR jet that
includes PISA shell, flow convergence and vena
contracta. Also obtain image of CWD thru mitral
valve, lining up with the regurgitant jet. Note the
timing of the peak velocity of MR jet.
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Bring up the MELAX view, and scroll to image that
shows PISA shell. Ideally, this should correspond to
the time of peak MR velocity.
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Zoom to magnify the image, adjust the color
Doppler baseline towards jet direction to achieve
an aliasing velocity of .30-.40 m/sec.
In the Measurement menu – find PISA MR under
the PISA folder.
Turn color off to visualize ventricular side of
orifice center.
Place cursor at this location to start radius measurement.
Turn color back on, and draw radius to PISA shell.
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Bring up CWD of mitral regurg jet. Find PISA MR
under the PISA folder.
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Trace MR curve. ERO and RV are calculated by
the machine.
EROA = 2 πr2 (VAliasing / Vmax)
EROA = 2 (3.14)(.8 cm)2 (.29 m/sec)/(4.35 m/sec)
EROA = .269 cm2
RV = EROA x TVImr = .269 cm2 x 137.9 cm
RV = 37.09 cm3
Note “rounding”
by the machine!
Putting it All Together:
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Jet Area: 7 cm2
Vena Contracta: .3 cm
EROA: .269 cm2
RV: 37 ml
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Jet Area: 7 cm2
Vena Contracta: .3 cm
EROA: .269 cm2
RV: 37 ml
Moderate MR (low end)
Notes:
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If you are doing calculations by hand, make sure
you convert units as needed.
Some machines use
cm/sec, others use
m/sec.
GE Vivid 7: m/sec
Notes:
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Use angle correction factor as needed:
Generally don’t need to correct central jets, but
becomes an issue with eccentric jets and also when
used in mitral stenosis.
 Multiply machine calculated EROA and RV by
(a/180) to get corrected numbers.
 If doing your own calculations, use this factor only
in the EROA calculation. Then this corrected
EROA x TVImr = corrected RV.
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Modifications:
Derivation of Angle Correction:
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If hemisphere is not complete because of
impingement by wall or leaflet (leading to a
funnel constraining flow), area of hemisphere is
modified:
Ahemisphere = 2πr2 (a/180)
Where a is the proximal flow convergence angle
Thus: EROA = 2 πr2 (VAliasing / Vmax) (a/180)
Modifications:
No CWD Measures
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If you can’t get a good CWD waveform, here is a
method to estimate EROA.
Set aliasing velocity to 40 cm/sec.
Assume Vmax = 500 cm/sec (This works when LV
systolic pressure is greater than left atrial pressure by
about 100 mm Hg)
EROA x Vmax = 2 πr2 x VAliasing
EROA = 2(3.14)r2 (40)/(500)
EROA = r2/2
Conclusions:
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We discussed basis of PISA
calculations.
Discussed pitfalls of PISA.
Showed an example how to do
PISA measurements with the
GE Vivid 7.
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In the end, one must integrate all the qualitative
and quantitative measures to come up with a
good MR severity assessment.
“It seems that we have a lot of room for
improvement, and that current echocardiographic
grading of MR severity is more art than science.”
Paul A. Grayburn, MD, Paul Bhella, MD 2010
References:
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Zoghbi WA, et al. Recommendations for Evaluation of the Severity of Native
Valvular Regurgitation with Two-dimensional and Doppler Echocardiography. J Am
Soc Echocardiogr 2003;16:777-802.
Lambert S. Proximal Isovelocity Surface Area Should Be Routinely Measured in
Evaluating Mitral Regurgitation: A Core Review. Anesth Analg 2007;105:940 –3
Shanewise JS. PRO: Proximal Isovelocity Surface Area Should Be Routinely Measured
in Evaluating Mitral Regurgitation. Anesth Analg 2007;105:947-8
Savage RM, Konstadt S. CON: Proximal Isovelocity Surface Area Should Not Be
Measured Routinely in All Patients with Mitral Regurgitation Anesth Analg
2007;105:944-6
Paul A. Grayburn, MD, Paul Bhella, MD Grading Severity of Mitral Regurgitation
byEchocardiography: Science or Art? JACC: Cardiovascular Imaging 2010. 3: 244-246
Biner S, Rafique A, Rafii F, et al. Reproducibility of proximal isovelocity surface area,
vena contracta, and regurgitant jet area for assessment of mitral regurgitation severity. J
Am Coll Cardiol Img 2010;3:235–43.