Download Strain Rate Imaging

TISSUE DOPPLER IMAGING
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 motion
Low velocity
• 5 to 20 cm/s
• 10 times slower than velocity of blood flow
High amplitude
• Approximately 40 decibels higher than blood
flow
IntJ 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 2dimensional 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 beamrelatively 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 LV
Filling 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 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 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.
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 planesrepresenting 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 cardiomyopathy
Dyssynchrony
Velocity vector imaging
Cardiac muscle
• 3 layers1) 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 diseaseDecreased 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
Hypertrophic
Cardiomyopathy
Normal longitudinal and other
types of strain
Decreased longitudinal strain
Increased LVEDV
Decreases after deconditioning for 3
months.
Decreased LVEDV
No change with deconditioning.
Increased LV twist.
Delayed LV untwisting.
Increased early LA strain rate.
Reduced LA strain and
strain rate