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

• Assessment of common stenotic lesions• MS• AS• TS• PS

BASIC CONSIDERATION

Volumetric flow calculations

D (h) = v x t D (h) =

D (h) =Area under curve=

VTI

Q= Cross sectional Area x VTI

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

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

Continuity equation

Limitations

• Limitations in measurement of flow

• Intracardiac shunts

• Regurgitation flow

• Low cardiac output

Bernoulli equation

• 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

P1, v1

P2, v2

Bernoulli equation & Pressure Gradients

Bernoulli equation & Pressure Gradients• Pressure recovery phenomenon


HR=72

HR=100

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


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

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


Angle correction• Flow can only converge

from an angle of a• Corrected Formulae MVA= 2pr2 x VN x a

Vorif 180


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

ASSESSMENT OF COMMON STENOTIC LESIONS

Mitral Stenosis

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

M-mode assessment

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

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 MSPHT> 220Mean Gradient >10

Mild Moderate Severe

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

Assessment of severity1. Funnel-shaped- Actual limiting

orifice at the tip

2. Instrumentation setting- ‘’blooming” of the echoes due to increased gain [operator—dependent]

3. Proper alignment of the imaging plane relative to valve orifice is critical

4. The orifice should be measured during initial diastole when the valve is maximally distended

5. Appropriate receiver gain settings are necessary

6. The orifice should appear fish mouthed

7. Good lateral resolution is necessary to identify the medial and lateral margins correctly.

8. Planimetry has decreased accuracy in the setting of valvular thickening and calcification, chest deformity and previous commissurotomy


Method for determining the correct level for planimetry

Step 1- Direct the scan plane to the level of papillary muscle

Step 2- Angle the transducer slightly medially & tilt superiorly until the tips of mitral leaflets are identified [ corres. to the smallest MVA]

Step 3- Freeze the image in early diastole

Step 4- Trace the MVA along the inner margins of the leaflets


Method for calculating the MVA by PHT & DT

Step 1- Optimize the CW Doppler Signal through the mitral valve [usually the best from apical window, colour flow imaging]

Step 2- Measure the peak E velocity [Vpeak]

Step 3- Determine the PHT point on the EF slope where V becomes Vpeak / 1.414

Step 4- Draw vertical lines from baseline to Vpeak & PHT point

Step 5- Measure the time interval between the vertical lines [= PHT]

Step 6- Trace the EF slope till it touches the baseline, measure the time interval from Vpeak to this point [=DT]

Step 7- Calculate MVA [220/PHT or 759/DT]

II. PHT or DT


PHT or DT TracingA normal range of PHT is 20 – 60msec

MS have PHT > 90msec


Method for calculating the MVA by PISA

Step 1- Zoom the area of the mitral valve from the apical four-chamber view.

Step 2- Use colour flow imaging of the mitral stenosis jet and upward shift of the zero baseline for colour map (30- to 45-cm/s aliasing velocity).

Step 3- Freeze colour flow images in a cine loop and identify an optimal frame to measure radius (r) of PISA in the LA.

Step 4- Determine the angle (a) between two mitral leaflets at the atrial surface and use the following formula: MVA= 2pr2 x VN x a Vpeak 180

III. PISA


Adjusting Aliasing velocity


Method for calculating the MVA by Continuity Equation

Step 1-Measure the CSA in cm2 of LVOT [ from PLAX view measure the LVOT Dia., during systole, inner edge to inner edge; CSA= 0.785 x D2]

Step 2- Measure VTI of LVOT [ from A5C view, PW doppler, SV just proximal to aortic valve, systole, trace leading edge velocity for VTI ]

Step 3- Measure VTI of MS [from A4C view, CW doppler, trace modal velocity VTI]

Step 4- Calculate MVA using the following formula: CSALVOT x VTILVOT

VTIMS

IV. Continuity Equation


Method for calculating the MV Gradients

Step 1-Optimize the CW Doppler Signal through the mitral valve [usually the best from apical window, colour flow imaging]

Step 2- Measure the peak E velocity [Vpeak]. Peak PG= 4 Vpeak2

Step 3- Trace the velocity signal of MS to get the mean PG.

Step 4- Mention the heart rate at which measurement taken

V. Pressure Gradients

TECHNIQUE METHOD REMARKS

Planimetry Measurement in short axis view

Operator dependent, decreased accuracy in setting of calcification or prev. commisurotomy

Pressure half time (Pt½ ) MVA= 220/ Pt½ where Pt½ =0.29 x Deceleration time

Unreliable in conditions with elevated LVEDP (MR, AI, recent PBMV)

Continuity Equation MVA=D2 LVOT x 0.785x TVI LVOT /TVI MV

In regurgitant lesions reliability decreases

PISA (Proximal Iso -velocity Surface Area)

MVA= 2πr2 x V Very reliable, operator dependent


Secondary features of MS

• LA dilation

• AF

• Spontaneous echo contrast

• LA thrombus

• Secondary pulmonary HTN-TR

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

Individuals with score≤8 –excellent for BMV

Those with score 12-less satisfactory results≧

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

Trileaflet valve

Normal valve area-3-4 cm²

Severity of Aortic Stenosis

AORTIC VALVE

Mild Moderate Severe

AVA-Direct planimetry

• Rarely are all 3 leaflets imaged perpendicular

• Triangular shape- measurement error

• Deformities & irregularities- further exacerbates

• AoV- superior-inferior rapid moments


Method for calculating the MVA by Continuity Equation

Step 1-Measure the CSA in cm2 of LVOT [ from PLAX view measure the LVOT Dia., during systole, inner edge to inner edge; CSA= 0.785 x D2]

Step 2- Measure VTI of LVOT [ from A5C view, PW doppler, SV just proximal to aortic valve, systole, trace leading edge velocity for VTI ]

Step 3- Measure VTI of AS [from multiple views , A5C view, CW doppler, trace modal velocity VTI]

Step 4- Calculate MVA using the following formula: CSALVOT x VTILVOT

VTIAS

I. Continuity Equation


Method for calculating the Pressure Gradients

Step 1-Optimize the CW Doppler Signal through the aortic valve [usually from apical 5C window, colour flow imaging]

Step 2- Measure the peak velocity [Vpeak]. Peak PG= 4 Vpeak2

Step 3- Trace the velocity signal of AS to get the mean PG.

Step 4- Mention the heart rate at which measurement taken

II. Pressure Gradients

Assessment of Severity

Discrepancies

– Technically poor doppler recording

– Non parallel interrogation angle

– Pressure gradients depends on HR, flow rate & valve narrowing –AR/LV dysfunction


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

Normal LV , AS

Abnormal LV , AS


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

AVA MACS

N > 2cm2 N > 15 mm

< 0.75 cm2 < 8 mm

> 1 cm2 > 12 mm

gray area 8 – 12 mm


• 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

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

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

Pulmonary stenosis

• Isolated or associated with other congenital lesions

• Jet velocity > 4 m/sec or maximum gradient > 60 mm Hg

• Prominent a waves in M-mode tracing

P V Pressure gradient A wave amplitude

Nil 2-7 mm

< 50 mm Hg 2-10 (6) mm

>50 mm Hg 6-18 (10) mm

Thank you

echocardiographic assessment of stenotic valvular lesions

Documents

2pr2 x vn x

x td h

2pr2 x vn qalias

p d2 x vtilvot

alvot x vtilvot vtipoint

aorif x vorif aorif

apoint x vtipoint apoint

chambers alvot x vtilvot