PISA Evaluation of

Mitral RegurgitationRaymond Graber, MD

Cardiac Anesthesia Group

University Hospitals Case Medical Center

4/07/2011

Introduction

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:

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?

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

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

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

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

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

The end result:

EROA = 2 πr2 (VAliasing / Vmax)

RVmr = EROA x TVImr

Assumptions:

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:

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?

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

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? :

Jet Area: 44%

Vena Contracta: 44%

EROA: 38%

Reasons for Variability of Assessments

> 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:

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

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.

Bring up the MELAX view, and scroll to image that

shows PISA shell. Ideally, this should correspond to

the time of peak MR velocity.

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.

Bring up CWD of mitral regurg jet. Find PISA MR under the PISA folder.

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:

Jet Area: 7 cm2

Vena Contracta: .3 cm

EROA: .269 cm2

RV: 37 ml

Jet Area: 7 cm2

Vena Contracta: .3 cm

EROA: .269 cm2

RV: 37 ml

Moderate MR (low end)

Notes:

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:

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.

Modifications:

Derivation of Angle Correction:

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

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:

We discussed basis of PISA

calculations.

Discussed pitfalls of PISA.

Showed an example how to do

PISA measurements with the

GE Vivid 7.

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: 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.