Transcript tissue doppler basics

TISSUE DOPPLER BASICS
DR BIJILESH U
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Tissue Doppler imaging (TDI) is a relatively
new echocardiographic technique that uses
Doppler principles to measure the velocity of
myocardial motion.
Assessment of myocardial motion
• 2D imaging
– Poor delineation of endocardial borders
– Inter observer variability
– Qualitative than quantitative
– Poor regional function assessment
– Diastolic function assessment limited
TDI
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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 lowintensity 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
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
• 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
Color TDI
• Color-coded representation of myocardial
velocities is superimposed on gray-scale 2dimensional 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 -endocardialepicardial 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 beamrelatively 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
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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 LV
Systolic 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 of
Diastolic 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 < 1
Em <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 LV
Filling 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 Between
Constrictive 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 of
Genetic 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’s
Heart 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 Cardiac
Dyssynchrony
• 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 Right
Ventricular 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
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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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