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’ 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 NameSize (µm)Shell compositionGas contentindication AI SYNTHETIC POLYMERPERFLUORO CARBON Myocardial perfusion CARDIOspere4.0POLYMER BILAYERNITROGENMyocardial perfusion DEFINITY (USA) Lipid encapsulatedPERFLUOROPRO PANE LV opacification OPTISON7 (USA) DENATURED ALBUMIN PERFLUOROPRO PANE LV opacification SONOVUE (EUROPE, ASIA) 2.5PHOSPHOLIPIDSSULPHUR 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 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 to 1.4 Low MI < 0.3

Contrast Destruction High Mechanical Index High Frame rate Focal zone Near field

FundamentalHarmonic

Continuous Imaging Low Mechanical IndexHigh 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 shuntNegative 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 1 st 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 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 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