Echocardiography PISA assessment Ppt Powerpoint Presentation slides Mark Wiley Medical Slideshow Echocardiography and LVAD assessment 2005 04 26

Echocardiography PISA assessment

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Notes

Show Notes

Slide 1 :

Pitfalls of PISA University of Kansas Medical Center

Slide 2 :

Proximal Isovelocity Surface Area Method An estimation of the regurgitant or stenotic mitral oriface Concept – based on the continuity equation As blood flow enters a regurgitant oriface it accelerates progressively and concentrically to produce a series of shells. These shells converge toward the regurgitant oriface maintaining a given amount of flow. Because blood flow in the flow convergence enters the oriface exclusively, the principle of conservation of mass can be applied to the flow through the oriface.

Slide 3 :

Proximal Isovelocity Surface Area Method (Hemispheric shells of flow) Velocity increases as flow converges on the regurtitant oriface.

Slide 4 :

Proximal Isovelocity Surface Area Method For any given oriface Area = Flow Velocity This is modified for regurgitant flow with PISA Regurgitant flow = PISA X Velocity PISA = Effective regurgitant oriface area = 6.28 X radius2 Velocity = velocity of the shell Enriquez-Sarano M, Seward JB, Bailey KR, Tajik AJ. Effective regurgitant oriface area:A noninvasive Doppler development of an old hemodynamic concept. J Am Col Cariol 1994;23;443-51. Vandervoort PM, Rivera M, Mele D, et al. Application of color Doppler flow mapping to calculate effective regurgitant Oriface area: an in vitro study and initial clinical observations. Circulation 1993: 88:1150-6. Vandervoort PM, Thoreau DH, Riveral JM, Levine RA, Weyman AE, Thomas JD. Automated flow rate calculation based On digital analysis of flow convergence proximal to regurgitant orifices. J Am Coll Cardiol 1993;22:535-41.

Slide 5 :

Proximal Isovelocity Surface Area Method Regurgitant flow rate=6.28 X radius2 X Aliasing velocity In mitral regurgitation, flow travels away from the transducer in the apical position. The blood flow converging toward the mitral regurgitant oriface is color coded blue until it reaches its negative aliasing velocity. This allows the identification of a hemisphere of blood flow with a known velocity.

Slide 6 :

Aliasing Velocity Aliasing - erroneous frequency estimation occurring when the sampling frequency is less than twice the frequency to be measured. Example – think of a single spoked wheel with the following speeds 1RPM, 2RPM, 3RPM, 4RPM, 5RPM, 6RPM,7RPM Then flash a light on the spinning wheel 6X per minute

Slide 7 :

Aliasing Velocity Schematic depiction of the origin of the aliasing phenomenon using a turning wheel. When the Nyquist limit is exceeded,aliasing occurs.

Slide 8 :

Slide 9 :

Proximal Isovelocity Surface Area Method Measuring the radius occurs at the origin the negative aliasing Interface at a given aliasing velocity. The higher the aliasing velocity setting the smaller the radius

Slide 10 :

Proximal Isovelocity Surface Area Method The rate of flow through a hemispheric shell is equal to the area of the hemisphere multiplied by the flow velocity (aliasing velocity) Area of a hemisphere = 6.28 X r2 Flow rate=6.28 X radius2 X Aliasing velocity

Slide 11 :

Proximal Isovelocity Surface Area Method

Slide 12 :

Changing your aliasing velocity

Slide 13 :

Measuring PISA

Slide 14 :

Pitfalls to Using the PISA Method Shape of the flow convergence -shape of regurgitant oriface Timing of the flow convergence measurement Obtaining accurate measurement during peak systole Motion artifact Mitral oriface accelerates away and towards during systole Setting the Aliasing Velocity Regurgitant flow rate is systematically overestimated furthest from the orifice and underestimated closest to the orifice because of progressive flattening of the flow convergence region. Accurately Measuring the radius Surrounding structures

Slide 15 :

Pitfalls Shape of the regurgitant oriface Regurgitant oriface shapes vary from patient to patient. Schema of PISA with slitlike and Crescentic orifaces. The shape of PISA is closer to circular with a crescentic oriface than with a slitlike oriface on the valvular surface. In the perpendicular axis the radius for the crescentic oriface is shorter than the slitlike oriface for the same degree of regurgitation.

Slide 16 :

Pitfalls Correction for oriface shape Hemielliptic method – ideally measuring three orthogonal radii simplified linear regression method

Slide 17 :

Pitfalls to Using the PISA Method Shape of the flow convergence -shape of regurgitant oriface Timing of the flow convergence measurement Obtaining accurate measurement during peak systole

Slide 18 :

Pitfalls Timing of the cardiac cycle As the ventricle contracts, dynamic changes occur in the mitral leaflets. Changes in the Effective Regurgitant oriface vary throughout the cardiac cycle. Does the maximum regurgitant jet represent the overall severity of regurgitant flow?

Slide 19 :

Pitfalls Timing of the cardiac cycle Mitral valve prolapse Maurice Enriquez-Sarano, Lawrence J. Sinak, A. Jamil Tajik, Kent R. Bailey, and James B. Seward Changes in Effective Regurgitant Orifice Throughout Systole in Patients With Mitral Valve Prolapse : A Clinical Study Using the Proximal Isovelocity Surface Area Method. Circulation 92: 2951-2958 Sequential changes in regurgitant velocity, effective regurgitant orifice (ERO), and regurgitant volume in patients with simple prolapse (left, n=9) or with flail leaflets (right, n=33), demonstrating a similar pattern of progression despite different degrees of regurgitation.

Slide 20 :

Pitfalls

Slide 21 :

Pitfalls - importance Phasic changes throughout the cardiac cycle may lead to an overestimation or underestimation of the overall severity of the effective regurgitant oriface.

Slide 22 :

Slide 23 :

Pitfalls The myocardium is dynamic Contraction accelerates initially away from the apical window. Difficulties with maintaining a perpendicular view during the cardiac cycle

Slide 24 :

Slide 25 :

Setting the aliasing velocity The higher the aliasing velocity setting the smaller the radius

Slide 26 :

Slide 27 :

Surrounding Structures

Slide 28 :

Surrounding Structures The PISA method is based on the assumption of a planar orifice with non-flail, symmetric mitral leaflets. For flail mitral leaflets, the proximal zone is constrained by the left ventricular wall and the convergence zone can no longer be modeled as a horizontal plane, since the angle subtended by the mitral leaflets is less than 180 degrees

Slide 29 :

Pitfalls - Surrounding Structures A correction formula is utilized To adjust for the given angle For any given scenario. The Formula corrects for the Area caculation for a hemisphere

Slide 30 :

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