Contrast Echocardiography

1. ContrastEchocardiography

2. Introduction • US contrast agents first used- mid 1970 • Gas containing microbubbles. • First generation Contrast Agents: Agitated saline with or without Indocyanine green.

3. 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

4. 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

6. Recent microbubble formulations

7. 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

8. Ultrasound Interaction with Contrast Agent >0.3 MI <0.3 MI

10. 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

11. Contrast Destruction • High Mechanical Index • High Frame rate • Focal zone • Near field

13. Fundamental Harmonic

14. Continuous Imaging Low Mechanical Index High Mechanical Index

15. 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.

16. Intermittent Triggered Imaging oIntermittent Imaging

17. Power Spectrum Motion of the bubbles & their resonance in a stationary field

18. Clinical Applications

19. 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

20. Exclusion of Thrombus

21. LV Thrombus

22. Ventricular noncompaction

24. 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

25. 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

26. Right-to-left shunt Negative contrast effect

27. Atrial septal aneurysm with PFO

28. Persistent Left SVC

29. 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

31. Time of appearance curve

32. 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

34. 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.

35. Transcatheter alcohol septal ablation

37. Attenuation & Shadowing

38. Papillary Muscle Shadow

39. Colour Artifact

40. Competitive Flow May be confused with a true negative contrast effect due to an atrial septal defect

41. 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

42. Strain Rate Imaging

43. 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

44. Strain & Strain rate

45. Strain calculated in three orthogonal planes- representing longitudinal, radial, circumferential contraction. • Negative strain- shortening of segment. • Positive strain- lengthening of segment

47. Methods

49. SR- Doppler tissue imaging

50. 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.