Intravascular Imaging Flashcards by George Burch

What is IVI?

Intravascular imaging

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What does IVI complements?

Conventional Angiography to further characterize plaque morphology and optimize performance of PCI

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What is the inherent limitations of imaging in Coronary Angiography

3 dimensional structure using a 2 dimensional lumenogram

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What is IVUS?

Intravascular ultrasound

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When was IVUS first developed and the first use? (2)

-1970s
-1988

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What is OCT?

Optical coherence tomography

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What is the current estimated usage of IVI in all PCI procedures?

<15%

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What does IVUS employ the use of?

Intravascular catheter mounted with a piezoelectric crystalline transducer to generate ultrasound pulses that provides real time 360 degree cross sectional images

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IVUS imaging offers characterization of what? (3)

-Intracoronary pathology
-Plaque morphology
-Vessel Wall architecture

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What are the engineering designs for IVUS? (2)

-Solid State
-Mechanical State

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What are solid state catheters composed of?

Phased array transducer elements in a circular manner at the distal tip

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What is the mechanical state catheter is composed of?

Rotating component for uniform signal transmission and acquisition

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What is the most common pull back method for IVUS?

Manual pull back

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What is the preferable pull back method and why?

-Automated Pull Back
-Pulls back at a constant rate which allows measurement of lesion length.

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What is the speed range of automatic pull back? (2)

-0.5 to 1.00 mm/s
-up to 10 mm/s in newer devices

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What does newer generation IVUS models range from in Mhz

20-60 MHz

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How is tissue penetration determined in IVUS (2)

-Frequency
-As frequency is increased, penetration distance is decreased.

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What can air bubbles in between the catheter sheath and IVUS transducer during rotation of mechanical catheters do?

Degrade the IVUS images

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What is the spatial resolution of IVUS in wavelength and beam width historically?

70 micrometers

What are OCT catheters designed to emit and recieve?

Near infrared light waves through a rotating single optical fiber and imaging lens.

What does OCT currently have? (3)

Highest resolution
-10-20 micrometers axial
-20-90 micrometers lateral

How many times greater are OCT to IVUS in imaging resolution but at what cost? (2)

-nearly 10 times greater
-At the expense of lower penetration depth (OCT 1-2 mm, IVUS 5-6 mm)

What is the use of OCT predication on?

Bloodless imaging through vessels have been cleared of blood by contrast

What can effect OCT images due to inadequate clearing of blood by contrast? (3)

-Ostial lesions
-Large or small vessels
-severe stenoses

What does IVUS not require unlike OCT?

Use of contrast for blood clearance

What is preferred in larger vascular structures such as the left main coronary artery?

IVUS due to enhanced tissue penetration in non calcified vessels

What cannot be accurately assessed with OCT?

Residual plaque burden at stent edges due to limited depth of penetration

What can be specifically helpful in treating patients with chronic kidney disease?

IVUS due to not requiring contrast

What can OCT resolution allow in stent restenotic lesions?

Further characterization including ability to detect neoatherosclerosis

Greater resolution of OCT enables what? (3)

-Precise locations of side branches, wire locations, and stent visualization

OCT is less prone to what?

Artifact

OCT affords the ability to do what in heavily calcified stenoses

Ability to measure and characterize

What is used to assess plaque composition and key lesions, and landing zones before intervention

IVI (Intravascular Imaging)

When should imaging be performed with administration of intracoronary nitroglycerine

After administration and should begin 20 mm or more distal to the area of interest and end at the LM or Right coronary artery ostium

What can be done if the imaging catheter fails to cross the lesion and PCI is planned?

Low pressure undersized balloon pre dilation or atherectomy to facilitate catheter passage

What does IVI improve for stents? (5)

-Detection -Localization -Quantification -Characterization -Expansion

What are the imaging strategies that are proposed for the selection of stent diameter? (4)

-Mean reference lumen -Largest reference lumen -Mean mid wall reference -Smallest reference external elastic lamina

What is the morphological characteristics associated with stent under expansion for IVUS? (4)

-Superficial calcium angle >270 degrees -360 degrees of superficial calcium -Calcified nodule -Vessel diameter <3.5 mm

What is the morphological characteristics associated with stent under expansion for OCT? (3)

Calcium angle >180 degrees Calcium thickness >0.5 mm Calcium length >5mm

Stent lengths should be selected to facilitate?

Complete lesion coverage from the most normal distal segment to the most normal proximal segment.

Stent expansion is a strong predictor of? (2)

Future stent patency and subsequent clinical events

What is postprocedure IVI used for?

-To confirm that optimal procedural endpoints -Exclude complications

When do minor edge dissections become clinically insignificant (2)

-<45 degree circumference -Measuring <2mm in length

What is malapposition?

Lack of contact of stent struts with the luminal surface area

What does acute stent malapposition typical result from?

Stent undersizing, most often from CTO lesions and ACS settings

When does stent under expansion occur?

Deploying an appropriately sized stent at subnominal pressure in the presence of of underlying resistant plaque.