Contrast Echocardiography DR PRASANTH S. Introduction US contrast agents first used- mid 1970 Gas...
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Transcript of Contrast Echocardiography DR PRASANTH S. Introduction US contrast agents first used- mid 1970 Gas...
Contrast Echocardiography
• DR PRASANTH S
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 indicationAI-700 2.9 SYNTHETIC POLYMER PERFLUORO
CARBONMyocardial perfusion
CARDIOspere 4.0 POLYMER BILAYER NITROGEN Myocardial perfusion
DEFINITY(USA)
1.1-3.3 Lipid encapsulated PERFLUOROPROPANE
LV opacification
OPTISON7(USA)
2.0-4.5 DENATURED ALBUMIN
PERFLUOROPROPANE
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 motion-not 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
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 & Strain rate
• Strain calculated in three orthogonal planes- representing 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 cardiomyopathyDyssynchrony
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