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Echocardiographic assessment of stenotic valvular lesions

Echocardiographic assessment of stenotic valvular lesions. Dr Nithin P G. Layout of seminar. Basic considerations Volumetric flow calculations Continuity equation Bernoulli equation & Pressure Gradients Pressure Half Time & Deceleration time Proximal Isovelocity Surface Area method

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Echocardiographic assessment of stenotic valvular lesions

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  1. Echocardiographic assessment of stenotic valvular lesions Dr Nithin P G

  2. Layout of seminar • Basic considerations • Volumetric flow calculations • Continuity equation • Bernoulli equation & Pressure Gradients • Pressure Half Time & Deceleration time • Proximal Isovelocity Surface Area method • Assessment of common stenotic lesions • MS • AS • TS • PS

  3. Basic consideration

  4. Volumetric flow calculations D (h) = v x t D (h) = D (h) = Area under curve= VTI Q= Cross sectional Area x VTI

  5. Volumetric flow calculations Limitations • Assumptions • Flow through rigid circular tube [elastic] • Uniform velocity across the vessel • Derived CSA is circular [AV valves elliptical] • CSA constant throughout the flow • SV remains in constant position throughout • Errors in VTI measurements • Inadequate beam alignment • Failure to correctly trace the VTI [ leading edge in A,P modal velocity in M,T] • 3-5 beats in SR, 8- 10 bts in AF • Incorrect gain settings and filter settings • Errors in diameter measurements • Wrong phase of cardiac cycle • Inconsistent annulus measurement

  6. Continuity equation • QLVOT= Qthru all chambers • ALVOT x VTILVOT = Apoint x VTIpoint • Apoint = ALVOT x VTILVOT VTIpoint = p D2 x VTILVOT 4 VTIpoint = 0.785 D2 x VTILVOT VTIpoint • No intracardiac shunts between the two points • No significant regurgitant flow

  7. Continuity equation Limitations • Limitations in measurement of flow • Intracardiac shunts • Regurgitation flow • Low cardiac output

  8. Bernoulli equation P1, v1 P2, v2 • D P= 4V2 • Peak Pressure Grad = 4 x (Vmax)2 • Mean PG = 4 x (∑V1²+V2²+…Vn²) n MPG=[∆P(max)/1.45 ]+2 MPG=2.4(Vmax)²

  9. Bernoulli equation & Pressure Gradients

  10. Bernoulli equation & Pressure Gradients • Pressure recovery phenomenon

  11. Bernoulli equation & Pressure Gradients

  12. Bernoulli equation & Pressure Gradients HR=72 HR=100

  13. Pressure Half Time & Deceleration time

  14. Pressure Half Time & Deceleration time • PHT- time required by the pressure to decay to half its original value [ velocity to V/1.414] MVA= 220/PHT • DT- Time taken for peak early diastolic velocity to fall to zero [ PHT= 0.29 x DT] MVA= 759/DT

  15. Pressure Half Time & Deceleration time Advantages • Not affected by low cardiac output • Not affected by coexisting MR Limitations • Affected by LV compliance, Peak Pressure gradients • Post BMV • Severe AR [elev. LVEDP shortens PHT] • Severe LVH- ↓LV compliance • Misinterpretation b/w AR velocity and MS signal [ MS after IVRT] • Prosthetic mitral valve- not validated

  16. Proximal Isovelocity Surface Area method • QAlias= AAlias x VAlias • QAlias= 2pr2 x VN • QAlias= QOrif = AOrif x VOrif • AOrif = 2pr2 x VN VOrif Stenotic orifice area

  17. Proximal Isovelocity Surface Area method Angle correction • Flow can only converge from an angle of a • Corrected Formulae MVA= 2pr2 x VN x a Vorif 180

  18. Proximal Isovelocity Surface Area method Advantages • Mitral valve calcification • MR/AR • Accurate and reliable Disadvantages • Peak velocity (E) rather than integration of flow over the entire diastolic period • Vena contracta= effective orifice area < anatomical orifice • Radius measurement calculation • Accurate measurement required • Low Aliasing velocity will reduce accuracy

  19. Assessment of Common stenotic lesions

  20. Mitral Stenosis

  21. Mitral Stenosis • RHD • Commissural fusion⇒doming/bowing • Chordal thickening ⇒ abnormal motion • Progressive fibrosis⇒stiffening ⇒calcification • Doming of the mitral valve (hockey stick AML) • Funnel shaped opening of mitral valves • Focal thickening and beading of leaflets • Calcification

  22. M-mode assessment Decrease in the initial diastolic leaflet closure (E-F slope) [>80mm/s⇒MVA =4-6cm², <15mm/s⇒MVA <1.3cm²]

  23. Severity of MS • The normal adult mitral valve area (MVA) is 4 to 6 cm² in CSA • Severe MS when, MVA of < 1.0 cm²- severe MS PHT> 220 Mean Gradient >10 Mild Moderate Severe

  24. Assessment of severity I. 2D-Planimetry • 2D short axis imaging of diastolic orifice-planimetry • Smallest orifice at the leaflet tips • Inner edge of the black/white interface traced • Correlates well with hemodynamic assessment

  25. Assessment of severity • Funnel-shaped- Actual limiting orifice at the tip • Instrumentation setting- ‘’blooming” of the echoes due to increased gain [operator—dependent] • Proper alignment of the imaging plane relative to valve orifice is critical • The orifice should be measured during initial diastole when the valve is maximally distended • Appropriate receiver gain settings are necessary • The orifice should appear fish mouthed • Good lateral resolution is necessary to identify the medial and lateral margins correctly. • Planimetry has decreased accuracy in the setting of valvular thickening and calcification, chest deformity and previous commissurotomy

  26. Assessment of severity

  27. Assessment of severity II. PHT or DT

  28. Assessment of severity PHT or DT Tracing A normal range of PHT is 20 – 60msec MS have PHT > 90msec

  29. Assessment of severity III. PISA

  30. Assessment of severity Adjusting Aliasing velocity

  31. Assessment of severity IV. Continuity Equation

  32. Assessment of severity V. Pressure Gradients

  33. Assessment of severity

  34. Secondary features of MS • LA dilation • AF • Spontaneous echo contrast • LA thrombus • Secondary pulmonary HTN-TR

  35. Echo approach to MS • Valve morphology, etiology • Exclude other causes of clinical presentation • MS severity Peak & Mean PG 2D valve area MVA by PHT, Continuity, PISA • Assosiated MR • LA enlargement/ clots • Pulmonary art pressure • Co-existing TR severity • Assessment for BMV

  36. Individuals with score≤8 –excellent for BMV Those with score≧12-less satisfactory results

  37. Tricuspid Stenosis • Normal inflow velocity < 0.5-1m/sec, mean gradient < 2 mm Hg. • Respiratory variation in inflow velocity [ increased during inspiration]. Best measured with breath held in expiration • 2D-Planimetry cannot be used • Severe when mean PG > 7 mm Hg or PHT > 190 msec

  38. AORTIC VALVE Trileaflet valve Normal valve area-3-4 cm² Severity of Aortic Stenosis Mild Moderate Severe

  39. AVA-Direct planimetry • Rarely are all 3 leaflets imaged perpendicular • Triangular shape- measurement error • Deformities & irregularities- further exacerbates • AoV- superior-inferior rapid moments

  40. Assessment of severity I. Continuity Equation

  41. Assessment of severity II. Pressure Gradients

  42. Assessment of Severity Discrepancies • Technically poor doppler recording • Non parallel interrogation angle • Pressure gradients depends on HR, flow rate & valve narrowing –AR/LV dysfunction

  43. Assessment of Severity Dobutamine Echo • Aortic valve area depends on Aortic flow rate • Distinguish- true severe valvular stenosis vs mild to mod stenosis with LV dysfunction • Stepwise infusion of dobutamine(5—30µg/kg/min) • Lack of contractile reserve- Failure of LVEF to ↑ by 20% is a poor prognostic sign

  44. Normal LV , AS Abnormal LV , AS

  45. Assessment of Severity Maximal aortic cusp separation (MACS) on M-mode Vertical distance between RCC and NCC during systole Stenotic Aortic Valve → decreased MACS Limitations • Single dimension • Asymmetrical AV involvement • Calcification / thickness • ↓ LV systolic function • ↓ CO status

  46. Assessment of Severity • Ao valve resistance- Has a good correlation with AVA for a given aortic velocity. Resistance=28/ AVA x √gradient( mean) =(∆P/∆Q)mean x1333 • Dimensionless index [DI] DI =VTILVOT / VTIAortic If DI < 0.25 for native valve, then critical stenosis

  47. Discrepancies in AS severity assessment AS by gradient Gradient lower than expected • Reduced EF • Significant MR Gradient higher than expected • Significant AR • High Output states like anemia, fever AS by continuity Equation • Associated subvalvular obstruction [higher LVOT velocities, abnormal measurements]; [AR not C.I.] • LVOT TVI- SV -just behind AoV • Suboptimal LVOT measurements • Low Trans Aortic flow rate Low EF Small ventricular chamber Mod-severe MR

  48. Echo approach to AS • Valve anatomy, etiology • Exclude other LVOTO • Stenosis severity • jet velocity • mean pressure gradient • AVA – continuity equation • LV Dimensions/ hypertrophy/ EF/ diastolic fn • Aorta Aortic diameter/ annulus diameter/ assess COA • AR – quantification if more than mild • Associated MR- mechanism & severity • Pulmonary artery pressure

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