PISA Evaluation of MR - Casecag.com

PISA Evaluation ofMitral RegurgitationRaymond Graber, MDCardiac Anesthesia GroupUniversity Hospitals Case Medical Center4/07/2011

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 withTwo-dimensional and Doppler Echocardiography. J Am Soc Echocardiogr 2003;16:777-802.In the OR, typical methods for MR evaluation include qualitativemeasures such as color jet area, chamber size, and pulmonary vein flow.Quantitative measures include vena contracta and measures of EROAand regurgitant volume.

Regurgitant ColorDoppler FlowPattern:• Distal jet.• Vena contracta• Proximal flowconvergence

Jet Area IssuesEvaluating color jet area would seem to be an easy thing to do, butthere are multiple caveats:• Assumes that regurgitant velocities correlates with regurgitantvolumes.• Is one point in time, whereas volume includes duration of flow.• Behavior of jet depends on receiving chamber – can beconstrained 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 40-50mm Hg in group A.Gain settings changed.

What is PISA?• PISA = Proximal Isovelocity Surface Area• A concept that can be used to help determinesize of a regurgitant or stenotic orifice.• Based on flow dynamics, use of aliasing andcontinuity principle.

Flow Dynamics 1• When fluid is forced from a chamber thru anorifice, the fluid accelerates towards the orifice,and velocity is greatest at the narrowest point ofthe orifice.

• With color Doppler, asflow accelerates towardsorifice – at some point,velocity may exceed thealiasing velocity, andcolor will reverse fromred to blue. At thishemisphere, the velocityis thus known (it equalsthe aliasing velocity).Use of Aliasing

Continuity Principle• Because of the conservation of mass principle, flowrate must remain constant along the length of a conduit(assuming the absence of any leaks or additional input)A 1 x V 1 = A 2 x V 2

Applying this to MR:Regurgitant Orifice Flow = Flow at hemisphereof color changeEROA x V orifice = A hemisphere V hemisphereV orifice =V max (by CWD)A hemisphere = 2πr 2V hemisphere = V AliasingEROA x V max = 2 πr 2 x V Aliasing

Assumptions:• Assumes accurate Doppler measurement of regurgitantvelocity.• Assumes regurgitant orifice is circular.• Assumes that the orifice is on a planar surface, and thatthe 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 velocityaccurately with Doppler?

Central jet: goodCWD curve.

Eccentric jet:suboptimalCWD curve.

Are Regurgitant Orifices Circular?This 3DTEE showsa regurgitantorifice that iselongated.

Rifkin and Sharma. Alternative Isovelocity Surface Model. J AC C : Cardiovascular Imaging 2010Other mathematicalmodels beingdeveloped for PISA innon-hemisphericalorifices.

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 AccurateMeasurement of Radius:• Adjusting the aliasingvelocity by shifting thecolor Doppler baselinetowards the directionof flow increases themeasured radius andimproves accuracy.

Is the Regurgitant OrificeConstant In Size?Orifices can changein size over time,especially withprolapse. It isrecommended to usethe PISA radius thatcorresponds to thetime of peakregurgitant velocity.

(J Am Coll Cardiol Img 2010; 3:235– 43)How good are these measurements? Can we agree upon them?

• In the ideal situationclinicians would look at ameasure, and all would agreethat the MR was severe, oragree that it was not. Yet inthis study, was not the case.For example, looking at Jetsize in patient 1, 39% rated itas severe, and 61% rated it asnot severe!

Cardiologist Agreement• The authors defined“substantial agreement” as>80% of cardiologists were inagreement with a finding for aspecific patient.• In what % of images was theresubstantial agreement? :• Jet Area: 44%• Vena Contracta: 44%• EROA: 38%

Reasons for Variability of Assessments• > 30% variation of PISA radius during thecourse of the MR jet: 44%• > 30% variation of VC width during thecourse of the MR jet : 44%• Effective MR orifice identifiable: 44%• Eccentric were much harder to evaluatequantitativly then central jets

Their Conclusions:• The VC and PISA measurements for distinction ofsevere versus non-severe MR are only modestly reliableand associated with suboptimal interobserveragreement.• The presence of an identifiable effective regurgitantorifice improves reproducibility of VC and a centralregurgitant jet predicts substantial agreement amongmultiple observers of PISA assessment.

Example: PISA Step By STEP

• Use MELAX view, obtain image of MR jet thatincludes PISA shell, flow convergence and venacontracta. Also obtain image of CWD thru mitralvalve, lining up with the regurgitant jet. Note thetiming of the peak velocity of MR jet.

• Bring up the MELAX view, and scroll to image thatshows PISA shell. Ideally, this should correspond tothe time of peak MR velocity.

• Zoom to magnify the image, adjust the colorDoppler baseline towards jet direction to achievean aliasing velocity of .30-.40 m/sec.

In the Measurement menu – find PISA MR underthe PISA folder.

Turn color off to visualize ventricular side oforifice 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 MRunder the PISA folder.

• Trace MR curve. ERO and RV are calculated bythe machine.

EROA = 2 πr 2 (V Aliasing / V max )EROA = 2 (3.14)(.8 cm) 2 (.29 m/sec)/(4.35 m/sec)EROA = .269 cm 2RV = EROA x TVI mr = .269 cm 2 x 137.9 cmRV = 37.09 cm 3Note “rounding”by the machine!

Putting it All Together:• Jet Area: 7 cm 2• Vena Contracta: .3 cm• EROA: .269 cm 2• RV: 37 ml

• Jet Area: 7 cm 2• Vena Contracta: .3 cm• EROA: .269 cm 2• RV: 37 mlModerate MR (low end)

Notes:• If you are doing calculations by hand, make sureyou convert units as needed.Some machines usecm/sec, others usem/sec.GE Vivid 7: m/sec

Notes:• Use angle correction factor as needed:• Generally don’t need to correct central jets, butbecomes an issue with eccentric jets and also whenused in mitral stenosis.• Multiply machine calculated EROA and RV by(a/180) to get corrected numbers.• If doing your own calculations, use this factor onlyin the EROA calculation. Then this correctedEROA x TVI mr = corrected RV.

Modifications:Derivation of Angle Correction:• If hemisphere is not complete because ofimpingement by wall or leaflet (leading to afunnel constraining flow), area of hemisphere ismodified:A hemisphere = 2πr 2 (a/180)Where a is the proximal flow convergence angleThus: EROA = 2 πr 2 (V Aliasing / V max ) (a/180)

Modifications:No CWD Measures• If you can’t get a good CWD waveform, here is amethod to estimate EROA.• Set aliasing velocity to 40 cm/sec.• Assume Vmax = 500 cm/sec (This works when LVsystolic pressure is greater than left atrial pressure byabout 100 mm Hg)EROA x V max = 2 πr 2 x V AliasingEROA = 2(3.14)r 2 (40)/(500)EROA = r 2 /2

Conclusions:• We discussed basis of PISAcalculations.• Discussed pitfalls of PISA.• Showed an example how to doPISA measurements with theGE Vivid 7.

• In the end, one must integrate all the qualitativeand quantitative measures to come up with agood MR severity assessment.“It seems that we have a lot of room forimprovement, and that current echocardiographicgrading 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 NativeValvular Regurgitation with Two-dimensional and Doppler Echocardiography. J AmSoc Echocardiogr 2003;16:777-802.• Lambert S. Proximal Isovelocity Surface Area Should Be Routinely Measured inEvaluating Mitral Regurgitation: A Core Review. Anesth Analg 2007;105:940 –3• Shanewise JS. PRO: Proximal Isovelocity Surface Area Should Be Routinely Measuredin Evaluating Mitral Regurgitation. Anesth Analg 2007;105:947-8• Savage RM, Konstadt S. CON: Proximal Isovelocity Surface Area Should Not BeMeasured Routinely in All Patients with Mitral Regurgitation Anesth Analg2007;105:944-6• Paul A. Grayburn, MD, Paul Bhella, MD Grading Severity of Mitral RegurgitationbyEchocardiography: 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. JAm Coll Cardiol Img 2010;3:235–43.