TISSUE DOPPLER BASICS

DR BIJILESH U

• Tissue Doppler imaging (TDI) is a relatively

new echocardiographic technique that uses Doppler principles to measure the velocity of myocardial motion.

• 2D imaging– Poor delineation of endocardial borders– Inter observer variability– Qualitative than quantitative– Poor regional function assessment– Diastolic function assessment limited

Assessment of myocardial motion

TDI

• TVI obtain data even in suboptimal 2D windows• Less inter observer variation• Quantitative than qualitative • Important in diastolic function assessment• Better regional assessment

Principles of TDI

Doppler Effect

Frequency of a reflected ultrasound wave is

altered by movement of the reflecting surface

away from or towards the source

Doppler tissue Vs blood pool imaging

• RBC s - relatively weak reflectors and fast moving

• Conventional doppler -filters adjusted to exclude highly reflective objects and to maximize less reflective & high velocity objects

• TDI- target is tissue rather than red blood cells. • Tissue has a greater reflectivity and slower

motion, • Filters set to exclude high velocities and low-

intensity reflectors. • Filters are set to parameters opposite

Limitations

• TDI measures only the vector of motion that is parallel to the direction of the ultrasound

• Incident angle between the beam and the direction of target motion varies from region to region

• Limits the ability to provide absolute velocity • Unable to discriminate passive motion from

active motion

Tissue Doppler –imaging modes

– Pulse wave Doppler– Color 2D imaging– Color M- Mode

Pulsed-wave TDI

• Used to measure peak myocardial velocities

• Suited to the measurement of long-axis ventricular motion

• Longitudinally oriented endocardial fibers are most parallel to the ultrasound beam

in the apical views.

• mitral annular motion :good surrogate measure of overall longitudinal left ventricular (LV) contraction and relaxation

• To measure longitudinal myocardial velocities, the sample volume is placed in the ventricular myocardium immediately adjacent to the mitral annulus

Wave forms

• The cardiac cycle is represented by 3 waveforms 1. Sa - systolic myocardial velocity above the

baseline as the annulus descends toward the apex

2. Ea - early diastolic myocardial relaxation velocity below the baseline as the annulus ascends away from the apex

3. Aa - myocardial velocity associated with atrial contraction.

PARAMETERS OF TDI

Normal Doppler pattern

• Septal Systolic velocities lower than free wall Sm• Em / Am more than one, similar to E/ A in mitral flow • Peak velocities at base and decrease towards apex• Age related reduction in peak velocities Sm and Em• Em/ Am reversal after age of 50

Sm (cm/sec) Em (cm/sec) Am (cm/sec)

Septal 8.7 + 1.4 12.3 + 2.9 8.9 + 2.4

Lateral 10.3 + 1.8 16.3 + 2.9 7.8 + 3.0

Color TDI

• Color-coded representation of myocardial velocities is superimposed on gray-scale 2-dimensional or M-mode images

• indicate the direction and velocity of myocardial motion

• increased spatial resolution and the ability to evaluate multiple structures and segments in a single view.

M-mode color Doppler tissue imaging

• Color -encoded images of tissue motion along an M-mode interrogation line

• Represents a combination of M-mode echocardiography, color Doppler imaging, and quantitative Doppler tissue imaging

• High temporal and spatial resolution • Determining velocity gradients between

adjacent points or more recently for strain rate imaging

Endocardial-epicardial gradient

• DTI sample volume in the subendocardium, & subepicardial

• Difference between velocities -endocardial-epicardial gradient.

• Alterations ,with a selective decrease in the subendocardial velocities --very sensitive marker of ischemia

• determined in a single segment with the same angle of interrogation of the Doppler beam- relatively angle independent

Strain

• Deformation of the myocardium on application of stress

• Change in distance between two points divided by the initial length (L0).

• expressed as percentage L-Lo• Lo • Strain rate :- rate of deformation• Integration of Strain Rate gives strain

Strain rate

• Derivative of DTI provides a high-resolution evaluation of regional myocardial function

• sensitive and earlier indicator of regional dysfunction

• With DTI simultaneously determine velocities in two adjacent points & relative distance in between

• Defined as the instantaneous rate of change in the two velocities divided by the instantaneous distance between the two points.

• Positive strain rate represents active contraction and negative values, relaxation or lengthening between the two points.

• Clinical Applications of TDI

Assessment of LVSystolic Function

• Systolic myocardial velocity (Sa) at the lateral mitral annulus measure of longitudinal systolic function

• Correlated with LV ejection fraction• Mitral annular displacement Velocity reduced in

LV dysfunction • Regional reductions in Sa - regional wallmotion

abnormalities. • Advantage in suboptimal echo window

Assessment ofDiastolic Function

• Mitral inflow patterns are highly sensitive to preload

• mitral valve inflow patterns to assess diastolic function remains limited

• TDI assessment of diastolic function is less load dependent

• Ea - reflects the velocity of early myocardial relaxation as the mitral annulus ascends during early rapid LV filling.

• Peak Ea velocity - measured from any aspect of the mitral annulus from the apical views

• Lateral annulus most commonly used• Septal Ea velocitiy slightly lower than lateral Ea

velocities

• Reductions in lateral Ea velocity to ≤ 8 cm/s in older adults indicate impaired LV relaxation

• Differentiates normal from a pseudonormal mitral inflow pattern

• Unlike conventional mitral inflow patterns, Ea is resistant to changes in filling pressure

Em / Am < 1Em <8 cm/sec

CAD

• Reduction in Sa velocity can be detected within 15 seconds of the onset of ischemia

• Ischemia low systolic and diastolic velocities– <7.5cm./sec LV wall velocity - WMA– Em/ Am reversal

TDI Stress Echo

• Incorporation of TDI measures of systolic function in exercise testing to assess for ischemia

• Peak Sa velocity increases with dobutamine and exercise and decreases with ischemia– Better identification of abnormal segments – Better reproducibility than standard Echo– Peak velocity < 5.5 cm/sec identify abnormal segments

» 96% sensitivity, 81% specificity Katz et al

• Novel Applications of TDI

Estimation of LVFilling Pressures

• LV filling pressures are correlated with the ratio of the mitral inflow E wave to the tissue Doppler Ea wave (E/Ea)

• E/lateral Ea ≥ 10 or E/septal Ea ≥ 15 -- elevated LV end-diastolic pressure,

• E/Ea ≤ 8 is correlated with a normal LV EDP

• E/Em > 10 predicted PCWP > 15 mm of Hg with 92% sensitivity and 82% specificity Nagueh et al

Differentiation BetweenConstrictive and

Restrictive Physiology• Constrictive pericarditis and restrictive

cardiomyopathy -- abnormal LV filling • In the absence of myocardial disease, Ea

velocities typically remain normal. • intrinsic myocardial abnormalities - impaired

relaxation and reduced Ea velocities.

Constriction Vs Restriction

• Em < 8 cm/sec restriction >8 constriction

» Garcia et al

Early Diagnosis ofGenetic Disease

• unexplained LV hypertrophy is typically required to diagnose hypertrophic cardiomyopathy (HCM)

• degree of hypertrophy and age of onset are highly variable

• Abnormalities of diastolic function-reduction of Ea velocities

• Sarcomere gene mutation ;before the development of LV hypertrophy

• Early stages of Fabry disease.

Differentiation of Athlete’sHeart From HCM

• Approximately 2% of athletes abnormal degree of LV hypertrophy

• Discriminating physiological hypertrophy due to intense athletic conditioning from pathological

• Athletes highly compliant ventricles with brisk Ea velocities

• reduced Ea velocities in individuals with HCM

Assessment of CardiacDyssynchrony

• Identifying patients who will benefit from cardiac resynchronization therapy which can improve heart failure

• TDI can be used to assess the relative timing of peak systolic contraction in multiple myocardial regions

• standard deviation of the time to peak contraction represents a measure of overall ventricular synchrony

• identify potential responders to cardiac resynchronization therapy

Assessment of RightVentricular Function

• important prognostic indicator in patients with heart failure and in postinfarction patients

• Reduced tricuspid annular velocities with TDI have been documented in a variety of disease settings

• Post inferior myocardial infarction chronic pulmonary hypertension, and chronic heart failure

TDI

• Consider complimentary to the std. Echo• Important in diastolic function assessment• TVI obtain data even in suboptimal 2D windows• Less inter observer variation• Quantitative than qualitative • Better regional assessment• Assessment of myocardial asynchrony

Strain rate imaging

• Better regional assessment than TVI• Better predictor of LV function than TVI• Better predictor of ischemia

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