Contrast Echocardiography
Introduction
• US contrast agents first used- mid 1970
• Gas containing microbubbles.
• First generation Contrast Agents:
Agitated saline with or without Indocyanine green.
Agitated Saline
• Agitating a solution of saline
between two 10-mL syringes
• Each of which contains 5 mL of
saline and 0.1 to 0.5 mL of
room air
• Forceful agitation through a
three-way stopcock creates a
population of microbubbles
• ‘Dose’- 1- 5 ml
Ideal contrast agent
•
•
•
•
•
Non-toxic
Intravenously injectable
Has to behave similarly to blood
Crosses pulmonary filter
Resistant to intravascular and intra-cardiac
pressures
• Stable throughout during the exam
• Improve the Doppler signal-to-noise ratio
Recent microbubble formulations
Name
Size (µm)
Shell composition
Gas content
indication
AI-700
2.9
SYNTHETIC POLYMER
PERFLUORO
CARBON
Myocardial
perfusion
CARDIOspere 4.0
POLYMER BILAYER
NITROGEN
Myocardial
perfusion
DEFINITY
(USA)
1.1-3.3
Lipid encapsulated
PERFLUOROPRO
PANE
LV opacification
OPTISON7
(USA)
2.0-4.5
DENATURED
ALBUMIN
PERFLUOROPRO
PANE
LV opacification
SONOVUE
(EUROPE,
ASIA)
2.5
PHOSPHOLIPIDS
SULPHUR
HEXAFLUORIDE
Myocardial
perfusion, LV
opacification
• Low surface tension.
• Resistant to ultrasound destruction.
• Slowly diffusing, insoluble, high molecular weight gases.
• 1.1 – 8 µm size, 5х10⁸ to 1.2x 10¹⁰ microbubbles per millilitre
• Single injection provide contrast effect for 3- 10 min.
• Safe – 4 deaths after 2 million use
• Contra indications
– Known Rt to Lt shunts
– Known hypersensitivity
Ultrasound Interaction with Contrast Agent
>0.3 MI
<0.3 MI
Machine settings
• Dedicated contrast specific presets
• Mechanical Index; Power of US beam
Peak Negative acoustic pressure
Transmitted Frequency
Routine B mode uses – High MI - 0.9 to 1.4
Low MI < 0.3
Contrast Destruction
• High Mechanical Index
• High Frame rate
• Focal zone
• Near field
Fundamental
Harmonic
Continuous Imaging
Low Mechanical Index
High Mechanical Index
Intermittent imaging
• Triggered to ECG
• In between imaging, no
ultrasound energy is
delivered.
• Allows time for restitution
of contrast effect.
• Analysis of wall motionnot possible.
• Evaluation of myocardial
perfusion.
Continuous low MI
imaging.
• Wall motion analysis in
real time.
• Used for cavity
opacification.
• Detection of very low
concentration of
myocardial contrast.
Intermittent Triggered Imaging
oIntermittent Imaging
Power Spectrum
Motion of the bubbles & their resonance in a stationary field
Clinical Applications
Detection and Utilization of Intracavitary contrast
• Enhanced visualization of the LV endocardial borders
• Improve reproducibility for wall motion analysis and
volumetric measurements
• Detection or exclusion of
– Intracavitary thrombus
– Ventricular noncompaction
– Atypical forms of HCM (Apical)
– Abnormal communication to the ventricular chamber
Exclusion of Thrombus
LV Thrombus
Ventricular noncompaction
Spectral Doppler Enhancement
• Low concentrations of contrast
agents
• Enhancing the tricuspid
regurgitation jet
• Pulmonary vein flow
• Increasing intensity of a relatively
weak aortic stenosis jet
Shunt Detection
• Right-to-left shunts - agitated saline - agent of choice
– Atrial septal defects of all types
– Patent foramen ovale - Valsalva and cough
– Pulmonary arteriovenous malformations -
5 to 15 cycles
– Larger ventricular septal defects during diastole
– Left SVC
• Left-to-right shunt
– Negative contrast effect
Right-to-left shunt
Negative contrast effect
Atrial septal aneurysm with PFO
Persistent Left SVC
Myocardial Perfusion Contrast
• First recognized in the 1980s
• Preserved contrast effect in the myocardium - evidence of
microvascular integrity and blood flow to the area
• Analysis of myocardial flow - Time of appearance curve
• Multiple time appearance curve analyses - necessary
• Time of appearance curve requires a bolus effect
– wait 10 minutes
– purposeful destruction of the contrast agent - burst of high intensity
(high mechanical index) ultrasound
• Targeted to different regions of interest
• Performed under basal conditions & after vasodilator stress
Time of appearance curve
• α is directly related to myocardial blood volume
• β is related to flow rate
• The product of α and β- proportional to myocardial blood flow
• Vasodilator results in an increase in flow velocity in those
areas not perfused by a stenosed artery
• Appearance of the contrast curves - differ in the normal and
diseased beds
Transcatheter alcohol septal ablation
• Performed for the Rx of HOCM.
• Catheter is placed in the 1st septal perforator of LAD.
• Controlled myocardial infarction for reduction of
proximal septal mass.
• Before alcohol injection, diluted US contrast agent is
injected to the selected artery.
• To ensure- no contrast reflux.
• To confirm the presence and size of vascular bed.
Transcatheter alcohol septal ablation
Attenuation & Shadowing
Papillary Muscle Shadow
Colour Artifact
Competitive Flow
May be confused with a true negative contrast effect due to an atrial septal defect
Prominent eustachian valve and margination of
contrast-enhanced blood flow
May be confused with a true negative contrast effect due to an atrial septal defect
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 & Strain rate
• Strain calculated in three orthogonal planesrepresenting longitudinal, radial,
circumferential contraction.
• Negative strain- shortening of segment.
• Positive strain- lengthening of segment
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.
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
VENTRICULAR TORSION
• Similar to the winding and Unwinding of a towel.
• Isovolumetric contraction the apex rotates clockwise
• Ejection phase apex rotates counterclockwise & base rotates
clockwise when viewed from the apex
• Diastole - relaxation of myocardial fibres - recoiling clockwise apical rotation.
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
Applications
• CAD- Myocardial ischemia, Myocardial infarction, Myocardial
viability.
• Heart failure with normal LVEF
• Cardiac resynchronization therapy (CRT)
• DCM
• HCM.
• Detection of subclinical diseases/early myocardial
involvement
Applications
• Stress cardiomyopathy
• Restrictive cardiomyopathy
• Detection of rejection and coronary stenosis in heart
transplant patients.
• Early detection of chemotherapy induced
cardiotoxicity.
• Valvular heart disease