copyright ©2013 american heart association intravascular ultrasound sripal bangalore, m.d., m.h.a....

Copyright ©2013 American Heart Association

INTRAVASCULAR ULTRASOUNDINTRAVASCULAR ULTRASOUND

Sripal Bangalore, M.D., M.H.A.and

Deepak L. Bhatt, M.D., M.P.H., F.A.H.A


OverviewOverview

Intravascular Ultrasound (IVUS) Rationale for use

Indications

Equipment

Technique

Image Interpretation

Qualitative Analysis

Quantitative Analysis

Artifacts


Rationale for useRationale for use

Limitations of angiography:

Under/over estimation of lesion extent and severity

Poor intra/inter observer correlation

Low resolution

Less sensitive to assess plaque characteristics

Two dimensional

Images the lumen and not the vessel wall

QCA measurements prone to magnification errors

Advantages of IVUS:

Precise quantification of disease extent and severity

Good intra/inter observer correlation

High resolution

Ability to assess plaque characteristics

360 degree measurement

Images the vessel wall

Accurate sizing of vessel


Class IIa IVUS is reasonable for the assessment of angiographically

indeterminate left main CAD. (Level of Evidence: B)

IVUS and coronary angiography are reasonable 4 to 6 weeks and 1 year after cardiac transplantation to exclude donor CAD, detect rapidly progressive cardiac allograft vasculopathy, and provide prognostic information. (Level of Evidence: B)

IVUS is reasonable to determine the mechanism of stent restenosis. (Level of Evidence: C)

IndicationsIndications

Levine GN, et al. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary intervention. Circulation. 2011;124:2574-2609.


Class IIb IVUS may be reasonable for the assessment of non–left main

coronary arteries with angiographically intermediate coronary stenoses (50% to 70% diameter stenosis). (Level of Evidence: B)

IVUS may be considered for guidance of coronary stent implantation, particularly in cases of left main coronary artery stenting. (Level of Evidence: B)

IVUS may be reasonable to determine the mechanism of stent thrombosis. (Level of Evidence: C)




Class III NO BENEFIT IVUS for routine lesion assessment is not recommended when

revascularization with PCI or CABG is not being contemplated. (Level of Evidence: C)




EquipmentEquipment

Mechanical IVUS System: A single rotating transducer

driven by a flexible drive cable

Smaller size compared to solid state systems

More artifacts – Guidewire, NURD, etc.

Higher resolution

Solid State System: Annular array of multiple

(64) imaging elements providing imaging by sequentially activating the imaging elements

Larger size compared to mechanical systems

Less artifacts

Ring-down artifact


TechniqueTechnique

Anticoagulation: bivalirudin or heparin as per routine clinical practice

6Fr guide catheter to engage the coronary ostium

Standard 0.014 inch guidewire to cross the lesion

Intracoronary nitroglycerin before acquisition of IVUS images to prevent artifacts from catheter induced coronary spasm

A well defined imaging protocol is vital for proper IVUS interpretation and reproducibility

Imaging should be acquired starting at least 10 mm distal to the lesion and preferably at the site of a branch vessel (as a reference marker) with pullback to the proximal vessel


TechniqueTechnique

Pullback using motorized transducer pullback (usually at 0.5 mm/s) can be used to survey the artery all the way back to the aorta

Manual transducer pullback can then be used to better interrogate areas of interest

The guiding catheter should be disengaged from the coronary ostium while interrogating an ostial lesion

The motorized pullback technique allows for L-mode (longitudinal) display and estimation of lesion length


Proximal and distal reference segments and the lesion should be identified

Proximal reference: The site with the largest lumen proximal to a stenosis but within the same segment (usually within 10 mm of the stenosis with no major intervening branches)

Distal reference: The site with the largest lumen distal to a stenosis but within the same segment (usually within 10 mm of the stenosis with no intervening branches)

Normal structures: Look for branches, veins and pericardium

Image Interpretation - QualitativeImage Interpretation - Qualitative


Image Interpretation - QualitativeImage Interpretation - Qualitative

Anterior Interventricular

Vein

Guidewire

IVUS Catheter

IVUS of Proximal LAD

1. Innermost layer (intima): Relatively echogenic compared with lumen or media and is comprised of intima, atheroma, and internal elastic lamina

2. Middle layer (media): Less echogenic than the intima

3. Outer layer (adventitia and periadventitial tissue): Relatively echogenic compared with media

Trilaminar Image

Intima

Media

Adventitia


Image Interpretation-QualitativeImage Interpretation-Qualitative

IVUS of LAD

Acoustic shadowing

Calcium

Branch vessel


Plaque CharacterizationPlaque Characterization

Soft Plaque - EccentricSoft Plaque - Concentric

Soft Plaque Hypoechoic compared to adventitia

High lipid content



Fibrous Plaque Similar/more echogenicity compared with adventitia

Rarely produce acoustic shadowing

Most common type of plaque


1800 Arc of Calcium 3600 Arc of Calcium

Fibrocalcific Plaque Hyperechoic compared to adventitia Acoustic shadowing seen 1800 of calcification must be present before it can be visualized by

angiography


Shadowing


ThrombusThrombus

Thrombus

Echolucent or variable grey scale appearance

Usually layered, lobulated, or pedunculated

Micro-channels are occasionally present

Diagnosis of thrombus by IVUS is always PRESUMPTIVE

Stent Strut

Thrombus

Subacute stent thrombosis (IVUS after mechanical thrombus aspiration)


Classification of Coronary Dissection

Intimal

Medial

Adventitial

Intramural Hematoma

Intra-stent

DissectionDissection

True Lumen (TL): 3-layer appearance (intima, media, adventitia); branches communicating with the lumen

False Lumen (FL): Not all layers are present; branches do not communicate with the lumen

Reproduced with permission from Ohlmann, P. et al. Circulation 2006;113:e403-e405

Angiographic and IVUS images of the LAD (1-4): Arrow points at the intimal flap. IVUS catheter is in the true lumen. The false

lumen is filled with contrast (black-image 1), blood (gray-image 4) and both contrast and blood (images 2 and 3)


Plaque RupturePlaque Rupture

Fibrous cap

Lipid core

Reproduced with permission from Tanaka, A. et al. Circulation 2002;105:2148-2152

Plaque rupture at the shoulder


Reproduced with permission from Rioufol, G. et al. Circulation 2004;110:2875-2880

A and B show ulcerated plaque. Follow up IVUS 21 months later shows the same ulcerated plaque (non healed).

Ulcerated PlaqueUlcerated Plaque


IVUS of LAD

Intramural HematomaIntramural Hematoma

Intramural Hematoma

Intramural Hematoma Accumulation of blood within medial space

Displacement of internal elastic membrane inwards and EEM outwards


True aneurysm:

Includes all layers of the vessel wall with an EEM and lumen diameter ≥ 50% larger than the proximal reference segment

Pseudoaneurysm:

Does not include all layers of vessel wall and with disruption of the EEM

AneurysmsAneurysms

Reproduced with permission from Noguchi, T. et al. Circulation 1999;99:162-163

Coronary angiogram and IVUS imaging of left circumflex artery

True Aneurysm

Prox Reference


Reproduced with permission from Oxford University Press - Ge, J. et al. EHJ 1999; 20: 1707–1716

The white arrows point to a ‘half-moon’ like crest shaped area of the bridge which maintains its shape during systole

Myocardial BridgeMyocardial BridgeDiastole Systole


Reproduce with permission from Shah, V. M. et al. Circulation 2002;106:1753-1755

Stent MalappositionStent Malapposition

Stent malapposition (white arrows): 1 or more struts clearly separated from vessel wall with evidence of blood speckles behind

the strut


Reproduced with permission from Tanabe, K. et al. Circulation 2003;107:559-564

Restenosis: Neointimal HyperplasiaRestenosis: Neointimal Hyperplasia

Neointimal hyperplasia in the gap between two stents

Neointimal hyperplasia

Stent Struts


Quantitative measurements are performed from “leading edge to leading edge”

Image Interpretation - QuantitativeImage Interpretation - Quantitative

EEM CSA

Lumen CSA

Maximal Lumen Diameter

Minimal Lumen Diameter

Max Plaque Thickness



Definitions Proximal reference: The site with the largest lumen

proximal to a stenosis but within the same segment (usually within 10 mm of the stenosis with no major intervening branches)

Distal reference: The site with the largest lumen distal to a stenosis but within the same segment (usually within 10 mm of the stenosis with no intervening branches)

Largest reference: The largest of either the proximal or distal reference sites

Average reference lumen size: The average value of lumen size at the proximal and distal reference sites



Definitions Lumen CSA: The area bounded by the luminal border Minimum lumen diameter: The shortest diameter through

the center point of the lumen Maximum lumen diameter: The longest diameter through

the center point of the lumen Lumen eccentricity: Max lumen dia - Min lumen diameter

Max lumen diameter

Lumen area stenosis: Ref lumen CSA - Min lumen CSA Ref lumen CSA

EEM CSA: The area bounded by the external elastic membrane border


Image Interpretation - QuantitativeImage Interpretation - QuantitativeDefinitions

Atheroma (plaque+media) CSA: EEM CSA - lumen CSA Max atheroma (plaque+media) thickness: The largest distance

from the intimal leading edge to the EEM Min atheroma (plaque+media) thickness: The shortest

distance from intimal leading edge to the EEM Atheroma eccentricity: (max atheroma thickness – min

atheroma thickness)/max atheroma thickness Atheroma burden: Plaque + media CSA

EEM CSA Remodeling index: Lesion EEM CSA

Ref EEM CSA

Remodeling index > 1.05 Positive remodeling Remodeling index < 0.95 Negative remodeling Remodeling index 0.95-1.05 No remodeling


Reproduced with permission from Dangas, G. et al. Circulation 1999;99:3149-3154

RemodelingRemodeling

Positive Remodeling

Negative Remodeling


Application IVUS (MLA) CFR FFR

Ischemia detection (proximal coronaries except Left Main and SVG)

< 2.7 - 4.0 mm2 < 2.0 < 0.75-0.80

Ischemia detection (Left Main)

< 6.0 mm2 < 2.0 < 0.75-0.80

Adequacy of stenting > 9.0 mm2

> 80% Reference Area

- ≥ 0.90*

≥ 0.94**


* Hanekamp et al. Circulation 1999;99:1015–21** Pijls et al. Circulation 2002;105:2950–4


Artifacts: NURDArtifacts: NURD

Non Uniform Rotational Distortion Seen with mechanical transducers and results from

mechanical binding of the drive cable that rotates the transducer (due to frictional forces)

Due to excessive vessel tortuosity, catheter twisting, calcified arteries, or excessive tightening of the hemostatic valve (O-ring)

Smudging of portions of the image

Fix: Loosening the O-ring


Artifacts: Ring-downArtifacts: Ring-down

Ring Down Artifact Produced by acoustic

oscillations in the transducer

Bright halos around the catheter

Creates a zone of uncertainty around the transducer

Less with solid state transducers

Fix: Adjusting the time gain control


Artifacts: Blood SpeckleArtifacts: Blood Speckle

Blood Speckle Artifact Due to increased transducer

frequency or decreased velocity of blood (in the region of severe stenosis)

Increased intensity of blood speckle makes delineation of lumen difficult as well as identification of plaques

Fix: Adjusting the time gain control or flushing the catheter with saline or contrast


Artifacts: GuidewireArtifacts: Guidewire

Guide Wire Artifact Seen mainly with

mechanical transducers

Acoustic shadow < 120 arc

copyright ©2013 american heart association intravascular ultrasound sripal bangalore, m.d., m.h.a....

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