TISSUE DOPPLER IMAGING
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Strain Rate Imaging
TISSUE DOPPLER IMAGINGDR PRASANTH SIntroduction TDI uses Doppler shift data from the myocardium to obtain qualitative and quantitative information on myocardial wall motion.Measures the velocity of myocardial wall motionLow velocity 5 to 20 cm/s 10 times slower than velocity of blood flowHigh amplitude Approximately 40 decibels higher than blood flowIntJ of Card Imaging 2001;17::8Doppler tissue Vs blood pool imaging
returning signal contains a broad range of frequency shifts with low-frequency shifts being related to slowly moving targets and high-frequency shifts to more rapidly moving targets. There is also a broad range in the signal amplitude with low-amplitude targets being represented by red blood cells and high-amplitude targets by tissue.3
blood motion imaging, low shifts and high-amplitude targets are filtered out, and a spectral display representing blood pool motion is presented. Opposite filtering of low-amplitude and high-frequency shifts results in selective registration of tissue motion.
4Tissue Doppler imaging modesPulse wave DopplerColor 2D imagingColor M- Mode
2D Colour TDIColour-coded representation of myocardial velocities- superimposed on gray-scale 2-dimensional 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.
Color TDI mode has the advantage of 6
septum moves posteriorly, it is encoded in blue, and as the posterior wall moves anteriorly in systole, it is encoded in red7M-mode colour Doppler tissue imaging Colour-encoded images of tissue motion along an M-mode interrogation line.High temporal and spatial resolution.
Pulsed-wave TDIUsed to measure peak myocardial velocities Mitral annular motion: Good surrogate measure of overall longitudinal left ventricular contraction and relaxation.To measure longitudinal myocardial velocities, the sample volume is placed in the ventricular myocardium immediately adjacent to the mitral annulus
TDI can be performed in pulsedwave and color modes.
Pulse Wave Tissue Doppler
Diastolic components of myocardial velocities correlate with mitral inflow velocities
Normal Myocardial Velocities : Basal Segments (cm/s)
J Am Soc Echo 2001;14:1143-52
Myocardial Velocity GradientDifference in myocardial velocity between the endocardium and epicardium divided by the myocardial wall thicknessReflects rate of change in wall thicknessMVG is an indicator of regional myocardial contraction.Determined in a single segment with the same angle of interrogation of the Doppler beam- relatively angle independentJ Am CollCard 1995; 26:217-23
Clinical Applications of TDI
Assessment of LV Systolic FunctionSa- Correlated with LV ejection fraction.Peak systolic velocities were measured at 4 different sites of the mitral annulus.A cut-off point of 7.5 cm/s had a sensitivity of 79 % and a specificity of 88 % in predicting preserved systolic function or ejection fraction of 0.50.Regional reductions in Sa - regional wall motion abnormalities. J Clin Basic Cardiol 2002; 5: 127
Regional Systolic Function
Pulse wave tissue Doppler after anteroseptal MI.Decreased velocity in the septum (top).Normal velocity in the lateral wall (bottom).
Impaired relaxationPseudonormalRestrictiveTransmitral flow velocities are dependent on LA filling pressures.Psuedonormalization occurs as LA pressure increases.Difficult to diagnose diastolic dysfunction from mitral flow velocities.
Myocardial velocities are persistently reduced in all stages of diastolic dysfunction.TDI assessment of diastolic function is less preload dependent.
Diastolic Dysfunction NORMALImpaired Relaxation Pseudonormal Restrictive Filling DT220 ms150-200 ms 8 < 8 < 8 < 8
Estimation of LVFilling PressuresLV filling pressures are correlated with the ratio of the mitral inflow E wave to the tissue Doppler Ea wave (E/E)
E/lateral E 20 - elevated LV end-diastolic pressure.
E/E = 5-15 is correlated with a normal LV EDP
E/E > 20 predicted PCWP > 15 mm of Hg with 92% sensitivity and 82% specificity Nagueh et al
Simultaneous cardiac catheterization and echocardiographic studies have shown that
23Constrictive Vs Restrictive PhysiologyConstrictive pericarditis with normal LV function have normal or elevated Em velocities.Doppler Em velocity of 8 cm/s differentiates constriction and restriction.Restrictive < 8 cm/sConstrictive > 8 cm/scharacteristic of restrictive cardiomyopathy result 24
Assessment of RightVentricular FunctionImportant prognostic indicator in patients with heart failure and in postinfarction patientsReduced tricuspid annular velocities with TDI have been documented in Post inferior myocardial infarction, chronic pulmonary hypertension, and chronic heart failure.The complexity of right ventricular anatomy and geometry challenges accurate assessment of right ventricular systolic function
26Limitations Accuracy of velocities dependent on angle of ultrasound beam.Not all wall velocity obtainable from every view.Wide range of normal values.Even non contractile myocardium will be pulled by near by segments resulting in apparent velocity component.
Strain Rate ImagingIntroduction Evaluation of a myocardial region with reference to an adjacent myocardial segment.
Deformation analysis- analysis of ventricular mechanics or shapes during cardiac cycle.
Myocardial strain, strain rate, torsion.
Strain- percentage thickening or deformation of the myocardium during the cardiac cycle.
Change of strain per unit of time is referred to as strain rate
Strain calculated in three orthogonal planes- representing longitudinal, radial, circumferential contraction.
Negative strain- shortening of segment.Positive strain- lengthening of segment
Strain & Strain rate
33Methods Comparison of Two-Dimensional Speckle Tracking Echocardiography(2D STE) with Tissue Doppler Imaging (TDI) 2D STE TDIDeformation analysis in 2 dimensions .One-Dimension measurementsAngle independentMeasurement dependent on angleBetter spatial resolutionLimited spatial resolutionLess time-consuming data acquisition and easy data processing.Time-consumingLower temporal resolutionHigh temporal resolutionDependent on high resolution image qualityImage quality less important Lower interobserver variabilityHigher interobserver variabilityLower optimal frame rate limits the reliability of measurements in patients with tachycardia
SR- Doppler tissue imaging
Speckle tracking Speckles are small dots or groups of myocardial pixels that are created by the interaction of ultrasonic beams and the myocardium.
Considered as acoustic fingerprint for that region.
This enables to judge the direction of movement, the speed of such movement, and the distance of such movement of any points in the myocardium.Speckle
MethodTrack the endocardial and epicardial borders of the left ventricleCorrectly dene the region of interest (ROI) in the long or short axis viewPost-processing software automatically divides the ventricle into six equally distributed segments2D or 3D data set is producedMathematical algorithms are applied to generate valuesStrain is not uniform among all myocardial segments.
Radial strain-Magnitude of basal parameters are higher than the apical values.Longitudinal strain- less variability fron apex to base.Circumferential strain- higher in anterior and lateral walls compared to posterior and septal.
Normal longitudinal strain averages -20%Normal radial strain about +40%
Normal Strain Displays Wave Forms ,Curved M-mode
Normal Strain Displays- bulls eye presentation
Normal pattern Dilated cardiomyopathyDyssynchrony
Velocity vector imaging
Cardiac muscle3 layers- middle transverse layer. inner oblique layer(descending segment) outer oblique layer( ascending segment)
VENTRICULAR TORSIONSimilar to the winding and Unwinding of a towel.Isovolumetric contraction -the apex and base rotates in counterclockwise direction.Ejection phase apex rotates counterclockwise & base rotates clockwise when viewed from the apexDiastole - relaxation of myocardial bres - recoiling - clockwise apical rotation.Isovolumetric relaxation- both apex and base rotates in clockwise direction.
Rotation - Measure of the rotational movement of the myocardium in relation to an imaginary long axis line from apex to base drawn through the middle of LV cavity.
Twist (degrees) is the net difference between apical and basal rotation
Torsion - Twist divided by the vertical distance between the apex and base and is expressed as degrees/cm.VENTRICULAR TORSION
CAD- Myocardial ischemia, Myocardial infarction, Myocardial viabilityReduction in strain by 2D STE more objective and accurate than the traditional visual method of assessing WMA.
Post systolic thickening (deformation)by radial strain correlates with the severity of ischemia.
To differentiate transmural from subendocardial infarction- lower circumferential strain in the formerApplicationsHeart failure with normal LVEF Reduced and delayed LV untwistingat rest and exerciseCardiac resynchronization therapy (CRT) Speckle Tracking and Resynchronization (STAR) study showed radial and transversal strain better than longitudinal and circumferential strain in predicting LVEF response and long term survival after CRT. Lack