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