Upload
stuart-fleming
View
218
Download
0
Tags:
Embed Size (px)
Citation preview
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
• THANKU