CC10: IVUS and OCT Flashcards
Uses of intravascular imaging
-Understand mechanism and pathophysiology of coronary syndromes
-Morphology of atherosclerotic plaques
-Optimise stent deployment
-Understand factors responsible in less optimal outcomes (e.g. stent thrombosis, sub deployment, restenosis)
Why is OCT not good for ostial left main disease?
-To inject contrast the catheter needs to be engaged
-Catheter will be in region of interest
How are IVUS images produced?
-Passing electrical current through a miniature transducer incorporated in tip of specialised catheter
-Transducer contains piezoelectric crystals
-Ultrasound reflected at interfaces between tissues or structures of different density
-Signal returns to transducer to create an electrical impulse
What does colour shading mean on IVUS?
-White signal = more reflection
-Black signal = less signal reflected
What are the 2 catheter types for IVUS?
Rotational IVUS
-single piezoelectric crystal with 1800rpm
-40-60MHz
-Min 5Fr
-Radiopaque markers to help guide lesion length
Phase array
-Multiple stationary placed piezoelectric transducers
-20MHz
-Plug and play - no catheter prep required
-Min 5Fr
-Radiopaque markers to help guide lesion length
Steps in performing IVUS
-Enter patient information on IVUS system
-Guide catheter and guide wire advanced
-Anticoagulation administered at therapeutic dose
-Nitrate given to optimise vessel size
-IVUS catheter advances distal to area of interest
-Go live and recording/pullback started
-Either manually or mechanically pulled back to proximal vessel
What are the views in IVUS?
Cross-sectional tomographic view
-Cross section 2D image of vessel lumen
Longitudinal view
-Useful review of plaque burden in vessel
-Useful for lengths (if using pullback sled)
Common lesions in IVUS?
-Calcium blocks US signals
-Appears very bright
Concentric vs Eccentric lesion
Concentric - lesion all the way round
Eccentric - lesion on one side
Types of artefact in IVUS
Ring Down artefact - common with phase array systems
-produced by acoustic oscillations in transducer
-gives bright artefact around catheter
Air artefact - common with rotational catheters
-Air in system, not flushed adequately
Non-uniform rotational distortion - hindered rotation
-can be present in bending or tortuous vessels
Reverberation
-strong reflectors (e.g. calcium, stents, guidewires/catheters may be reflected back and forth to transducer
-Displayed as layers
Indications for IVUS?
-Is lesion significant?
-Distal vessel diameter - what size stent?
-Proximal vessel diameter - how much to post dilate?
-Is there ostial disease?
-Associated with large branches?
What does post PCI IVUS check?
-Good sizing between stented region and non-stented
-Not stenting into area of disease
-Stent well deployed
What is shown here?
-Guidewire artefact
How do you treat malapposed stent?
-Post dilation balloon
Air and calcium on IVUS
-Air is dark
-Calcium is bright
Things to look out for in IVUS
ST elevation
-If lesion is significant, catheter may obstruct flow
-Flushing catheter when intra-coronary may give air embolus
Blunting of arterial pressure
-If using a 5Fr system
-If using a 6Fr system with multiple wires
What is OCT?
-General principle of operation similar to IVUS
-OCT uses infrared rather than ultrasound
-Infrared light has greater image resolution, but less tissue penetration
-High resolution images
-But more limited on depth (not appropriate for large vessels)
Features of OCT catheter
Rotational catheter
-Always need to connect to pullback device
-Needs to be pulled back at fast speed due to blood clearance
-Infrared light does not travel through blood so contrast is used
Why is IVUS used over OCT?
-OCT uses contrast
-Contraindicated in renal disease
In what situations is OCT less effective?
May produce poor quality images in ostial lesions LMS/RCA
-poor contrast flushing
-less effective in large vessels
Highly tortuous vessels, high calcium burden, severe stenosis
-Hard to advance catheter
-May interfere with blood clearance
Steps in OCT
1) Enter patient information on OCT machine
2) Cover pullback doc with sterile bag
3) Remove OCT catheter from sheath
4) Purge catheter with 100% contrast using purge syringe
5) Connect catheter to pullback doc
6) Recommend to check live view functioning prior to insertion
Guide wire/guide catheter in OCT?
Guide catheter
-Preferable 6F for contrast injection
-Needs good coaxial alignment to facilitate effective and safe contrast injection
-Guide wire positioned distally
-Ensure full anticoagulation
What are the lengths of acquisition in OCT?
-54 or 75mm pullback length
54mm - high definition, slower pullback (3.0 secs)
75mm - faster pullback speed (2.1 secs)
What are the types of pullback in OCT?
Manual or automatic
-Manual needs operator and controller both ready to ensure good pullback
-Automatic will pullback when contrast is detected
