pediatric echo measurements technique z score

EVALUATION OF CHAMBERS AND METHODS TO OBTAIN QUANTITATIVE INFORMATION IN PEDIATRICS

ByShivendra Kumar Yadav

Cardiac TechnologistKLE’s Dr Prabhakar Kore Hospital &MRC

BELGAUM

Outline

• Optimization techniques in imaging and Doppler evaluation

• Pediatric quantification protocols • Z scores

OPTIMAIZATION TECHNIQUES IN IMAGING

AND DOPPLER EVALUATION

Lets see what are the standard views to be obtained

SUBXIPHOID/SUBCOSTAL

APICAL PARASTERNAL SUPRASTERNAL

Long axis 4 chamber Long axis Long axis

3 chamber Short axis

Short axis 2 chamber High left parasaggital

Short axis

Ductal

RIGHT PARASTERNAL – HIGH RIGHT PARASTERNAL

ASE 2010

• Quantitative assessment of each structure should be performed in multiple views, and orthogonal planes should be used for noncircular structures such as AV valves.

• Current guidelines for chamber, annular and vessel quantification involve measurements of intra-luminal dimensions FROM ONE INNER EDGE TO THE OPPOSITE INNER EDGE

Measuring the Diameters

• Points to focus Vascular diameters should be perpendicular to

the long axis of the vessel Valvular and vascular diameters should be

measured at the moment of maximum expansion. IVC diameter- during exhalationMV & TV annulus- during diastoleAV & PV annulus – during systole

• Color mapping should precede spectral Doppler interrogation to identify the direction of flow.

• Doppler wave forms should be displayed at a sweep speed of 100 to 150mm/s to discriminate temporal changes in the velocity flow profile , particularly in children's with high heart rates.

• All Doppler measurements should be averaged over 3 consecutive cycles to account for respiratory variation.

PEDIATRIC QUANTIFICATION

PROTOCOLS

Inflows to Heart

• Pulmonary veins • Best evaluated in suprasternal short axis {crab

view}• Dual display with low scale color mapping

helps identify the individual pulmonary veins

The LA appendage should not be mistaken as LUPV.

The right middle pulmonary vein should not mistaken as RUPV{RUPV can be better identified in subxiphoid view}

Doppler evaluation of PV• pulmonary venous S,D&Ar

wave volocities and Ar wave normal duration is best measured in apical or parasternal short axis views

• Tip- sample volume should be placed >5mm from its ostium {because venous flow velocities are low}

SVC AND IVC

• IVC can be measured above its junction with the hepatic veins just below the diaphragm in subxiphoid short-axis {displaying IVC}.

• The utility of collapsibility index in children has not been evaluated.

• SVC flows can be evaluated in subxiphoid and suprasternal views

• IVC flows can be best evaluated in subxiphoid veiw.

SVC IS NOT MEASURED IN ROUTINE PRACTICE AND NORMATIVE DATA HAVE NOT BEEN ESTABLISHED.

LEFT ATRIUM

• The recommended methods to assess LA size include the measurement of major axis lengths in apical 4 chamber views

• Planimetered areas in orthogonal apical views• {just before the mitral valve opens}• Calculations of volumes using biplane area

length method or the Simpson method.

RIGHT ATRIUM

• The recommended methods to assess RA size include the measurement Of major axis and minor axis lengths.

• Planimetered areas in apical 4chamber view {at end systole just before tricuspid valve opens}

ATRIOVENTRICULAR VALVES

• Measurement helps to characterize valvar pathology and to diagnose ventricular hypoplasia.

• Recent studies suggest that both the valves lateral diameter should be assessed in apical 4 chamber view and anteroposterior diameter in parasternal long axis view.

THE LARGEST DIAMETERS DURING PEAK FILLING IN EARLY DIASTOLE SHOULD BE

MEASURED AT FRAME AFTER MAXIMUM EXCURSION OF THE LEAFLETS FROM INNER

EDGE TO INNER EDGE AT THE HINGE POINTS OF THE LEAFLET ATTACHEMENTS.

• Binder et al {2000} compared with 3D planimetric assessment in patients with mitral stenosis, 2D planimetry overestimates MV area by as much as 88%, depending on valve geometry.

• The recommended calculation for AV valves area should be done by using the formula for an ellipse.

Doppler evalutaion of AV valves

• Best performed with the help of color mapping in apical views• When there is stenosis VTI of the inflow tracing from continues

wave Doppler should be obtained • The pressure half time, continuity equation and other methods

are limited by faster heart rates in children • The recommended methods to assess MV inflow include

measurements of-E wave and A wave velocities A wave duration Deceleration time and IVRTCalculation of the E/A ratio

Assessment of LEFT VENTRICLE

• Two approach to asses1. A linear approach – includes a. measurements of short axis diameters b. Wall thickness c. Calculation of shortening fraction2. The volumetric approach- includesd. Measurement of areas from 2D or 3D short axis images e. Measurement of long axis lengthsf. Calculations of volumes, EF and mass.

Measurement of LV

LV should be measured both in systole and diastole.Short axis measurements and septal and posterior wall thickness can be obtained in parasternal view.

• Shortening fraction can be calculated using LV short axis internal diameters obtained from standard M-mode tracing or from 2D images using the equation

• SF= EDD-ESD EDD

CALCULATION OF VLOUME {AREA LENGTH METHOD}

SIMPSON METHOD

• Recommended Doppler evaluation of LV is with TDI

Medial and lateral annulus of mitral valve -peak e’, a’ and s’ velocities - IVRT , IVCT - E/e’ ratioIn children annular velocities are best measured

with a sample volume gate length of <5mm.

Assessment of RIGHT VENTRICLE

• The RV is technically difficult to evaluate by echocardiography because of its anterior retro-sternal position.

• The recommended methods to assess RV size include measurement of

end-diastolic diameters at the basal and midcavity levels,

end-diastolic and end systolic planimetered areas in apical 4 chamber views.

• To asses RV systolic function recommended methods are TAPSE and fractional area change.

• When tissue Doppler evaluation is performed is performed at tricuspid valve annulus, the recommended measurements and calculation include

- Peak e’, a’, And s’ velocities - IVRT

Ventricular outflow tracts and semilunar valves

• The transducer imaging plane should be parallel to the outflow tract long axis and magnification of the region of interest should be used.

• LVOT diameter is measured in parasternal long axis view during early to mid-systole.

• RVOT is diameter has been variably measured in parasternal short axis and long axis.

• Aortic valve and pulmonary valve annulus Best measured with magnification in

parasternal long axis views from inner edge to the proximal valve insertion hinge point within the arterial root to the inner edge of the opposite hinge point.

Can calculate stroke volume and cardiac output.

The maximum instantaneous and mean gradients along the LV outflow tract are best measured in

- apical 3 chamber - suprasternal long axis or right parasternalThe gradients along the RV outflow tract are best

measured in - subxiphoid short axis - parasternal long axis - parasternal short axis

In addition • The severity of pulmonary valve stenosis may

not be accurately assessed when a large VSD or PDA results in equalization of ventricular and arterial pressures.

• In the setting of ventricular dysfunction or a large shunting lesion, abnormalities in semilunar valve morphology and annular size are useful.

AORTA

• Measurements helps to identify patients with diverse vascular abnormalities, such as marfan syndrome and Kawasaki disease

• Should be measured at the maximum expansion, typically at peak flow during mid-systole.

• Proximal aorta is frequently dilated in marfan syndrome or a bicuspid aortic valve.

Sites of measurement of aorta

•Level of the aortic root•Sinotubular junction •Ascending aorta

In mid systole in parasternal long axis viewHigh right/left parasternal

view

•The proximal arch•Distal transverse arch•Aortic isthmus

In mid systole in suprasternal long axis view

Descending aorta Diameter in subxiphoid view

• Doppler evaluation helps to find the obstruction.• Aortic arch should be evaluated in a suprasternal long

axis view with step by step pulse wave Doppler interrogation.

• This gives the first clue of aortic arch obstruction.• The normal pattern reveals a brisk upstroke and return

to baseline.• Blunting with delayed or no return to baseline is an

important indicator of significant obstruction proximal to sample site.

PULMONARY ARTERY

• The main, right and left pulmonary arteries are best measured during mid-systole in parasternal , high left parasternal or suprasternal short axis view.

• In normal neonates, the branch pulmonary arteries are often relatively narrow, or originating at a slightly more acute angle.

• Pulse wave Doppler should be done at origin of each branch.

Z scores

• Z-scores are a means of expressing the deviation of a given measurement from the size or age specific population mean.

• By taking account of growth or age, Z-scores are an excellent means of charting serial measurements in pediatric cardiological practice.

Z-SCORES VERSUS CENTILES

• Many pediatricians and pediatric cardiologists are familiar with centiles, particularly with regard to patient height and weight. The relationship between centiles and Z-scores, for a normally distributed parameter, is shown in the use of either means of expression assumes a normal distribution of the data.

The relationship of Z-scores and centiles, assumingNormal distribution of the parameter. Note that the centile remainsvirtually constant at values distant from the mean (typically over 3standard deviations from the mean), whilst the Z-score continuesto be sensitive to changes in measurements

DILATEDHYPOPLASTIC

• For most measurements, the recommendation has been to calculate Z-scores with respect to patient body surface area rather than height or weight alone.

• Many formulas have been used to calculate body surface area including those of Boyd, Dubois and Dubois and Haycock, and it should be noted that there is considerable discrepancy in the values derived by each formula, particularly at low body size.

• BSA [m2] = 0.024265 weight [kg] x height [cms]

DERIVATION OF Z-SCORES

• A Z-score is defined as Z =( x− μ) δ

where χ is the observed measurement, m is the expected measurement (population mean) and s is the standard deviation of the population. Thus, Z-scores above the population mean have a positive value and those belowthe population mean have a negative value. The Z-score value conveys the magnitude of deviation from the mean.

For example, where the mean size of the aortic valve is 20mm, with a defined standard deviation of 3 mm, the Z-score of an aortic valve with annulus 14 mm is: z= 14-20/ 3 = -6/3 = -2

C Kampmann et al 2000

C Kampmann et al 2000

C Kampmann et al 2000

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