TISSUE DOPPLER IMAGING

DR PRASANTH S

Introduction

• 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::8

Doppler tissue Vs blood pool imaging

Tissue Doppler –imaging modes

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

2D Colour TDI

• Colour-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.

M-mode colour Doppler tissue imaging

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

• High temporal and spatial resolution.

Pulsed-wave TDI• Used 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

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 Gradient

• Difference in myocardial velocity between the endocardium and epicardium divided by the myocardial wall thickness

• Reflects rate of change in wall thickness• MVG is an indicator of regional myocardial

contraction.• Determined in a single segment with the same

angle of interrogation of the Doppler beam- relatively angle independent

J Am CollCard 1995; 26:217-23

CLINICAL APPLICATIONS OF TDI

Assessment of LV Systolic Function

• Sa- 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).

Diastolic Dysfunction

Impaired relaxation Pseudonormal Restrictive

• Transmitral 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

NORMAL Impaired Relaxation

Pseudonormal Restrictive Filling

DT <220 ms >220 ms 150-200 ms <150

E/A 1-2 <1 1-2 >2

Em > 8 < 8 < 8 < 8

Diastolic Dysfunction

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/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

Constrictive Vs Restrictive Physiology

• Constrictive 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/s• Constrictive > 8 cm/s

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

Limitations • 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 Imaging

Introduction

• 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

Methods

Doppler tissue imaging

• Two discrete points are compared for change in velocity• Strain rate- primary parameter obtained• Strain –derived by integrating velocity over time.

Speckle tracking

• Actual location of discrete myocardial segments calculated. • Strain is the primary parameter.• Strain rate-derived by calculating change in distance over time.

Comparison of Two-Dimensional Speckle Tracking Echocardiography(2D STE) with Tissue Doppler Imaging (TDI)

2D STE TDI

Deformation analysis in 2 dimensions . One-Dimension measurements

Angle independent Measurement dependent on angle

Better spatial resolution Limited spatial resolution

Less time-consuming data acquisition and easy data processing.

Time-consuming

Lower temporal resolution High temporal resolution

Dependent on high resolution image quality Image quality less important

Lower interobserver variability Higher interobserver variability

Lower 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

Method

• Track the endocardial and epicardial borders of the left

ventricle

• Correctly define the region of interest (ROI) in the long or

short axis view

• Post-processing software automatically divides the

ventricle into six equally distributed segments

• 2D or 3D data set is produced

• Mathematical algorithms are applied to generate values

• Strain 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 muscle• 3 layers-1) middle transverse layer.2) inner oblique layer(descending segment)3) outer oblique layer( ascending segment)

VENTRICULAR TORSION

• Similar 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 apex

• Diastole - relaxation of myocardial fibres - recoiling - clockwise

apical rotation.

• Isovolumetric relaxation- both apex and base rotates in

clockwise direction.

Myocardial mechanics

• 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 viability

• Reduction 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 former

Applications• Heart failure with normal LVEF

Reduced and delayed LV untwisting—at rest and exercise

• Cardiac 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 of dyssynchrony before CRT by 2D STE radial strain associated with death or hospitalization for heart failure

Twist in DCM

Am J Cardiol 2008;101:1163–1169, 2008

Applications • Stress cardiomyopathy.• Restrictive cardiomyopathy.• Detection of subclinical diseases/early myocardial

involvement.• Detection of rejection and coronary stenosis in heart

transplant patients.• Early detection of chemotherapy induced cardiotoxicity.• Valvular heart disease- Decreased radial, circumferential and longitudinal strain in

patients with severe aortic stenosis and normal LVEF. Long term follow up after valve replacement showed significant improvement in strain.

Differentiation of Athlete’s Heart from Hypertrophic Cardiomyopathy

Athlete’s Heart HypertrophicCardiomyopathy

Normal longitudinal and othertypes of strain

Decreased longitudinal strain

Increased LVEDVDecreases after deconditioning for 3 months.

Decreased LVEDVNo change with deconditioning.

Increased LV twist. Delayed LV untwisting.

Increased early LA strain rate. Reduced LA strain andstrain rate