OCT in intervention cardiology managment.pptx

OCT

1. Optical Coherence Tomography ( OCT ) Ahmed Galal, M.D. National Heart Institute

2. Introduction Coronary Angiography technique is restricted to a 2-D representation of the lumen without providing information about the vessel wall which is the substrate of atherosclerosis. This limitation led to the development of new intracoronary techniques which are able to image directly the atherosclerotic plaque. The introduction of intravascular ultrasound (IVUS) allowed a much more detailed evaluation of coronary atherosclerosis, but its limited resolution precluded the visualization of certain microstructures.

3. Introduction (Cont’d)

4. Optical Coherence Tomography (OCT) is a light-based imaging modality that can provide in-vivo high-resolution images of the coronary artery with a level of resolution ten times higher than IVUS but with a penetration depth limited to 1.5-2 mm. The technique uses low-coherent near infrared light to create high-resolution cross sectional images of the vessel. OCT, originally described in the early 1990s, was first applied in the field of ophthalmology and the vascular application was initiated in the mid 90s. Introduction (Cont’d)

5. Principle Intravascular OCT requires a single fiber optic wire that both emits light and records the reflection while simultaneously rotating and being pulled back along the artery. The coronary OCT light source uses a bandwidth in the near-infrared spectrum with central wavelengths ranging from 1,250 to 1,350 nm. WAVELENGTH – The distance over which the wave’s shape repeats.

6. Principle (Cont’d) The process is similar to that of ultrasonography, except that invisible light is used instead of sound waves.

7. Time Domain (TD) OCT Frequency Domain (FD) OCT Types of OCT

8. Introduction of FD analysis was a key milestone toward clinical viability of intravascular OCT as it significantly decreased the time of OCT imaging and eliminated the need to temporarily occlude the investigated segment in order to clear it from the blood. Therefore, current systems of intravascular OCT imaging employ only FD analysis. TD OCT FD OCT

9. Technique of OCT Console

10. Technique of OCT (Cont’d) Rapid exchange (Rx) imaging catheter. Contrast flush; balloon occlusion not required.

11. Technique of OCT (Cont’d)

12. Technique of OCT (Cont’d)

13. Drive Motor Controller (DOC)

14. PRIOR TO STARTING A CASE Required Materials: Imaging catheter Sterile DOC cover 3 ml purge syringe Contrast media indicated for coronary use 0.014" guidewire Guide catheter (6-7 F, with no sideholes )

15. Turning On the system and entering patient data. Catheter Preparation Purge with contrast until 3-5 drops exit distal tip. Remove the hoop carefully from the catheter. CONNECT CATHETER. Insert the DOC into the sterile bag. Inside the patient: Pullback preparation Purge the catheter. If blood enters the catheter lumen, purge with the attached 3 cc contrast syringe. PRIOR TO STARTING A CASE (Cont’d)

16. Preparation of Injection Recommended Settings: Injection by hand. Left coronary, Right coronary arteries. When the operator is ready to inject contrast, click the “Enable Pullback ” button. Ask the Physician to inject, 3 ml from the injection and when the image is clear press ”Start Pullback”. Performing the procedure. PRIOR TO STARTING A CASE (Cont’d)

17. Image Display “B-Mode” cross-sectional view “L-Mode” longitudinal view

18. OCT Image Interpretation Terminology Backscatter The reflection of light waves off the tissue and back to the catheter. High backscatter means a brighter pixel  Also described as a “ signal rich ” region. Low backscatter means a darker pixel  Also described as a “ signal poor ” region. Attenuation The reduction in intensity of the light waves as they pass through tissue due to absorption or scattering. High attenuation means the light cannot penetrate very deep. Low attenuation means the light can pass through to allow visualization of deeper tissue.

19. Composition Homogeneous: Uniform in structure. Heterogeneous: Structure consists of dissimilar elements. Texture Coarse. Fine. OCT Image Interpretation Terminology (Cont’d)

20. Image Analysis Normal coronary artery morphology In a healthy vessel OCT visualizes three layers of the artery: An internal elastic lamina (an abluminal bright, high reflective line). A media (a dark, low-reflective line). And an external elastic lamina (an adluminal high reflective zone). Beyond the external elastic lamina, OCT exposes an adventitia with its vasa vasorum.

21. Image Analysis (Cont’d)

22. Branches During OCT imaging, branches of any size and variable take‐off angle are easily detected.

23. Atherosclrosis LIPIDIC PLAQUE   FIBROTIC PLAQUE  CALCIFIED PLAQUE  Signal strength Low signal  High signal Low signal Signal homogeneity  Homogeneous  Homogeneus Inhomogeneous Plaque margins  Moderately delineated Poorly delineated  Well delineated Light attenuation High   Low   Low  Deep penetration Low   High    High

24. A and B calcified plaques. C Fibrous plaques. D lipid plaque

25. Plaque characterization of OCT images (optical frequency-domain imaging systems: top , and frequency-domain OCT: bottom ). Fibrous plaques exhibit homogeneous, signal-rich (highly backscattering) regions ( left , arrow ); lipid-rich plaques exhibit signal-poor regions with poorly defined borders ( middle , arrow ); and calcified plaques exhibit signal-poor regions with sharply delineated upper and/or lower borders ( right , arrow )

26. Vulnerable Plaque Detection Optical coherence tomography is now a gold standard to detect vulnerable plaques that are prone to rupture. Such plaques present with the following features: a thin fibrous cap (< 65 µm), a lipid rich core, neovascularization, and macrophage infiltration. All these features are reliably detectable by OCT, and especially the precise measurement of the thin fibrous cap (TCFA) is now possible due to OCT's superior resolution.

27. OCT is able to detect white and red thrombus inside the arterial lumen. The white thrombus appears as an irregular structure of high reflectivity and low attenuation of the signal. The red thrombus is shown as an irregular structure of low reflectivity and high attenuation of the signal. The more the thrombus caused shadowing and poor visibility of the structures behind it, the redder it is. Vulnerable Plaque Detection (Cont’d)

28. Vulnerable Plaque Detection (Cont’d)

29. Imaging of PCI Outcomes OCT is irreplaceable in terms of immediate and long-term analysis of PCI outcomes. Due to its high resolution it enables unparalleled insight into: Stent apposition, Stent expansion, Stent edge dissections, Protrusion of the plaque through struts, In-stent thrombosis.

30. Coronary stents by OCT. (a) Stent struts (arrows) are visible before luminal blood clearance. (b) Stent follow up case with typical strut distribution pattern. (c) Commercially available stent strut appearance consists of blooming (arrow) and shadow (star). Imaging of PCI Outcomes (Cont’d)

31. Malapposition Stent struts are defined to be malapposed when stent struts do not touch the vessel wall. The extent of the malposition is defined by its arc and by its length. Small malappositions are covered by the neointima and do not require any correction. However, a significant malapposition (> 200 µm) is a risk factor of acute in-stent thrombosis.

32. Dissections Edge dissection is defined as a disruption of the luminal vessel surface in the edge segment (within 5 mm proximal and distal to the stented region). Dissection in the stented segment is a disruption of the luminal vessel surface, with a visible dissection flap in the segment covered by the stent struts.

33. OCT. Top: Longitudinal view of the OCT pullback showing a region with an intimal flap (arrow). Bottom: Consecutive cross‐sectional images of the intimal flap.

34. 1) Homogeneous pattern of ISR. 2) Heterogeneous patterns subsequently subdivided in three subtypes: 2a) Layered pattern; 2b) Patchy pattern; and 2c) Speckled pattern. 3) Neo-atherosclerosis and its main features: 3a) Lipid plaque; 3b) Calcium deposit; 3c) TCFA; and 3d) Detail of macrophage presence in a lipid plaque. 4) Miscellaneous ISR characteristics: 4a) Microvessels ; 4b) Peri-strut low intensity areas; 4c) Overlapping stents; and 4d) Malapposed struts. 

35. Limitations of OCT An additional volume of contrast is unavoidable for OCT imaging, and hence it should be applied in patients with renal insufficiency carefully. Effective contrast injection requires the guiding catheter to intubate the coronary ostium, and that limits the analysis of ostial lesions. OCT image analysis is not free from artifacts, and therefore its results depend strongly on the observer's experience. Limited nIR light penetration depth hinders OCT application in vessels of more than 4 mm in diameter and impedes the comprehensive analysis of the plaque burden in the presence of significant positive remodeling where the external elastic lamina is quite remote from the lumen edge.

36. Limitations of OCT (Cont’d) Artifacts : Residual blood: Attenuates the OCT light (Swirling artifact) Sew-up Artifactis : Result from rapid artery or imaging wire movement leading to misalignment of the lumen border.

37. OCT vs IVUS Both OCT and IVUS may improve PCI outcomes. The benefits of intravascular imaging guidance may be greatest in high-risk patients and complex lesions, and in those with stent failure. IVUS and OCT do differ, each possessing important advantages and limitations, and whether OCT is superior to IVUS (or vice versa) in optimizing PCI outcomes is unknown. All interventionalists should become familiar with at least 1 of these 2 modalities based on individual preference and availability.