INTRAVASCULAR ULTRASOUND
Sripal Bangalore, M.D., M.H.A.
and
Deepak L. Bhatt, M.D., M.P.H., F.A.H.A
Copyright ©2013 American Heart Association
Overview
 Intravascular
Ultrasound (IVUS)

Rationale for use

Indications

Equipment

Technique

Image Interpretation

Qualitative Analysis

Quantitative Analysis

Artifacts
Copyright ©2013 American Heart Association
Rationale for use
Limitations of angiography:
Advantages of IVUS:

Under/over estimation of lesion
extent and severity

Precise quantification of
disease extent and severity

Poor intra/inter observer
correlation

Good intra/inter observer
correlation

Low resolution

High resolution

Less sensitive to assess plaque
characteristics

Ability to assess plaque
characteristics

Two dimensional

360 degree measurement

Images the lumen and not the
vessel wall

Images the vessel wall

QCA measurements prone to
magnification errors

Accurate sizing of vessel
Copyright ©2013 American Heart Association
Indications
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)
Copyright ©2013 American Heart Association
Levine GN, et al. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary
intervention. Circulation. 2011;124:2574-2609.
Indications
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)
Copyright ©2013 American Heart Association
Levine GN, et al. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary
intervention. Circulation. 2011;124:2574-2609.
Indications
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)
Copyright ©2013 American Heart Association
Levine GN, et al. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary
intervention. Circulation. 2011;124:2574-2609.
Equipment
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
Copyright ©2013 American Heart Association
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
Technique

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
Copyright ©2013 American Heart Association
Technique

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
Copyright ©2013 American Heart Association
Image Interpretation - Qualitative

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
Copyright ©2013 American Heart Association
Image Interpretation - Qualitative
Anterior
Interventricular
Vein
IVUS
Catheter
Guidewire
Intima
Media
Adventitia
IVUS of Proximal LAD
Trilaminar Image
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
Copyright ©2013 American Heart Association
Image Interpretation-Qualitative
Acoustic
shadowing
Calcium
Branch vessel
IVUS of LAD
Copyright ©2013 American Heart Association
Plaque Characterization
Soft Plaque - Concentric
Soft Plaque - Eccentric
Soft Plaque

Hypoechoic compared to adventitia

High lipid content
Copyright ©2013 American Heart Association
Plaque Characterization
Fibrous Plaque

Similar/more echogenicity compared with adventitia

Rarely produce acoustic shadowing

Most common type of plaque
Copyright ©2013 American Heart Association
Plaque Characterization
Shadowing
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
Copyright ©2013 American Heart Association
Thrombus
Thrombus
 Echolucent or variable
grey scale appearance
 Usually layered,
lobulated, or
pedunculated
Stent Strut
Thrombus
 Micro-channels are
occasionally present
 Diagnosis of thrombus by
IVUS is always
PRESUMPTIVE
Subacute stent thrombosis
(IVUS after mechanical
thrombus aspiration)
Copyright ©2013 American Heart Association

Dissection
Classification of
Coronary Dissection

Intimal

Medial

Adventitial

Intramural Hematoma

Intra-stent
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)
Reproduced with permission from Ohlmann, P. et al. Circulation 2006;113:e403-e405

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
Copyright ©2013 American Heart Association
Plaque Rupture
Plaque rupture at
the shoulder
Fibrous cap
Lipid core
Reproduced with permission from Tanaka, A. et al. Circulation 2002;105:2148-2152
Copyright ©2013 American Heart Association
Ulcerated Plaque
A and B show ulcerated plaque. Follow up IVUS 21 months later shows the same
ulcerated plaque (non healed).
Reproduced with permission from Rioufol, G. et al. Circulation 2004;110:2875-2880
Copyright ©2013 American Heart Association
Intramural Hematoma
Intramural
Hematoma
IVUS of LAD
Intramural Hematoma

Accumulation of blood within medial space

Displacement of internal elastic membrane inwards and EEM outwards
Copyright ©2013 American Heart Association
Aneurysms

Includes all layers of
the vessel wall with an
EEM and lumen
diameter ≥ 50% larger
than the proximal
reference segment

Prox
Reference
True aneurysm:
True
Aneurysm
Pseudoaneurysm:
Does not include all
layers of vessel wall
and with disruption of
the EEM
Coronary angiogram and IVUS imaging of left circumflex artery
Reproduced with permission from Noguchi, T. et al. Circulation 1999;99:162-163
Copyright ©2013 American Heart Association
Myocardial Bridge
Diastole
Systole
The white arrows point to a ‘half-moon’ like crest shaped area of the
bridge which maintains its shape during systole
Reproduced with permission from Oxford University Press - Ge, J. et al. EHJ 1999; 20: 1707–1716
Copyright ©2013 American Heart Association
Stent Malapposition
Stent malapposition (white arrows): 1 or more struts clearly
separated from vessel wall with evidence of blood speckles behind
the strut
Reproduce with permission from Shah, V. M. et al. Circulation 2002;106:1753-1755
Copyright ©2013 American Heart Association
Restenosis: Neointimal Hyperplasia
Neointimal
hyperplasia
Stent
Struts
Neointimal hyperplasia in the gap between two stents
Reproduced with permission from Tanabe, K. et al. Circulation 2003;107:559-564
Copyright ©2013 American Heart Association
Image Interpretation - Quantitative

Quantitative measurements are performed from
“leading edge to leading edge”
EEM CSA
Lumen CSA
Maximal
Lumen
Diameter
Minimal
Lumen
Diameter
Max Plaque
Thickness
Copyright ©2013 American Heart Association
Image Interpretation - Quantitative
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
Copyright ©2013 American Heart Association
Image Interpretation - Quantitative
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
Copyright ©2013 American Heart Association
Image Interpretation - Quantitative
Definitions






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
Copyright ©2013 American Heart Association
Remodeling
Negative Remodeling
Positive Remodeling
Reproduced with permission from Dangas, G. et al. Circulation 1999;99:3149-3154
Copyright ©2013 American Heart Association
Image Interpretation - Quantitative
Application
IVUS (MLA)
CFR
FFR
< 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
-
≥ 0.90*
Ischemia detection
(proximal coronaries except
Left Main and SVG)
> 80% Reference Area
* Hanekamp et al. Circulation 1999;99:1015–21
** Pijls et al. Circulation 2002;105:2950–4
Copyright ©2013 American Heart Association
≥ 0.94**
Artifacts: 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
Copyright ©2013 American Heart Association
Artifacts: 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
Copyright ©2013 American Heart Association
Artifacts: 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
Copyright ©2013 American Heart Association
Artifacts: Guidewire
Guide Wire Artifact
 Seen mainly with
mechanical transducers

Acoustic shadow < 120 arc
Copyright ©2013 American Heart Association