coronary imaging

Coronary Imaging

Dr. Mahendra

Cardiology,JIPMER

Coronary angiography

Gold standard for evaluating CAD

Guide both PCI and CABG

Provides highly useful picture of the vessel lumen

Indirect information about the arterial wall

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57/M ,old IWMI, CSA 3

FFR = 0.91

LM STENTING DEFERRED !!!

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Anatomical assessment

Intracoronary imaging

Functional assessment

FFR

?

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Muller et al., The Year in Intracoronary ImagingJ A C C : C A R D I O V A S C U L A R I M A G I N G ,

V O L . 3 , N O . 8 , 2 0 1 0

A U G U S T 2 0 1 0 : 8 8 1 – 9 1

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IVUS Image integrity should be

checked before inserting

No coronary preparation is needed

Iv Heparin 5000-10000U ;

Ic NTG 100-200 µ

Standard coronary interventional techniques and equipment (guiding catheter and 0.014 inch angioplasty guidewire)

Automated pullback device (usually at a rate of 0.5–1.0 mm/s for any length) or by manual operator pull back

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Characteristic three-layered

appearance (bright-dark-bright)

Spillover effect (blooming)

Normal vessel – intima maynot be

seen

Atherosclerotic vessel – media

may not appear distinct

20-45 MHz

100-200 µ resolution

4-8 mm beam penetration

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Minimal lumen dimension

Maximal lumen dimension

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Lumen area

Total vessel area

Plaque area

Neointimal hyperplasia

Plaque burden = plaque area

total vessel area

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Reference segment – most normal looking (largest

lumen with smallest plaque burden) within 10 mm

from the lesion with no intervening side branches

Arterial remodelling (Glagov et al)

-Positive remodelling (adaptive);RI >1

-Negative remodelling(constrictive);RI<1

-Intermediate remodelling

Remodelling Index = EEM surface area (lesion site)

EEM surface area (reference site)

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Gray scale IVUS

Soft plaque – echogenicity less than the

surrounding adventitia

Fibrous plaque – intermediate echogenicity

between those of soft plaques and highly

echogenic calcium plaques

Calcified plaques – high echogenicity with

acoustic shadowing (superficial or deep)

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Plaque characterization24

Dark green - fibrous

Light green - fibrofatty

White- calcium

Red - necrotic

Green – fibrous

Yellow – dense fibrous

Blue- lipid pool

Red- calcium

Green - fibrotic

Yellow- lipidic

Light blue- calcium

Pink - necrotic

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Abnormal lesion morphology27

Interventional applications Angiographically intermediate lesions

Calcified lesions – degree and location

High risk lesions for distal embolisaton –lipid pool and thrombus containing

Left main lesions (<6 mm2) – LITRO

Bifurcation lesions

CTO

ISR

Optimal device sizing (angiographic normal reference segment vs IVUS reference segment) – CLOUT, BEST, STILLR

Opimal stent expansion – CRUISE, AVID

Acute stent problems ( Incomplete expansion, malapposition, marginal tears )

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Vulnerable plaque

Hypoechoic plaques without a well formed fibrous

caps

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Plaque rupture

Hypoechoic cavity within the plaque is connected

within the lumen and a remnant of fibrous cap is

observed at the connecting site

Often eccentric, less calcified, large plaque burden,

positively remodelled, and a/w thrombus

Extensive positive remodelling – most consistent

feature reported in GS-IVUS predicting plaque

instability

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Ability of IVUS to predict future coronary events

- PROSPECT trial

Three vessel VH-IVUS in 697 ACS patients

Three baseline IVUS characteristics that

independently predicted future events

1) Plaque burden > 70 %

2) TCFA

3) MLA < 4 mm2

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Safety

Most frequent acute complication – transient

coronary spasm 1-3%

Major complications <0.5% (Dissections,

thrombosis, abrupt closure)

Batkoff BW, Linker DT, Safety of intracoronary ultrasound:

data from a Multicenter European Registry, Cathet

Cardiovasc Diagn, 1996;38:238–41.

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Limitations Extensive calcification at lesion site leads to large

acoustic shadowing and difficulty in interpreting the

exact size of the vessel

Ghost images - Occurs when structures of high

echogenicity are imaged (eg Calcium, stent struts).

Appear on the side of the transducer that is opposite

the bright structure being imaged.

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A case with spontaneous dissection. Optical coherence

tomography (C) visualized spontaneous dissection that could not

be found with angiography (A) or intravascular ultrasound (B).

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OCT

Optical analogue of IVUS

Significantly higher resolution (10 times more) but

lesser penetration

Uses near infrared rays- 1.3 microns

OCT measures the time delay of the light that is

reflected or backscattered from tissue, and that is

collected by the catheter, by using a technique

known as interferometry.

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IMAGING WIRE AND CATHETER

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TD- OCT FD-OCT

• Injecting continuous saline/contrast flushes through theguiding or delivery catheters.

•Proximal balloon occlusion ofthe vessel with distalsaline/contrast injection.

•Time-consuming

• Require a high degree ofoperator expertise

•FD OCT systems do not requireproximal occlusion

•Bolus injection of saline, contrast, orotherSolution, injected at rates of 2 to 4ml/s, and an automated 20 mm/spullback within a monorail rapidexchange catheter allows imaging of a6-cm-long coronary segment during a3-s injection

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NORMAL ARTERIAL WALL IN OCT38

1)Fibrous plaques -- homogeneous, signal-rich regions

2)Fibro - calcific plaques --- signal-poor regions/ sharp borders

3)Lipid-rich plaques ---signal-poor regions with diffuse borders

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Ex vivo validations --- OCT superior to conventional andintegrated backscatter IVUS for the characterisation ofcoronary atherosclerotic plaque composition.

In vivo, OCT is superior for the identification of lipidpools

Thin capped fibroatheromas (TCFA) - defined pathologically by the triad of:

Lipid core.

Fibrous cap with a thickness < 65 micron m.

Cell infiltration of the fibrous cap.

OCT for in vivo assessment of fibrous cap thickness ----Unique ability to image superficial detail.

OCT can quantify macrophages within the fibrous cap.

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OCT can identify intracoronary thrombus and plaque rupture with high accuracy.

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OCT AND PCI Fine resolution at a superficial depth, OCT allows a

uniquely detailed image of the effects of stent

implantation on the vessel wall.

OCT allows:

Examination of the target vessel both pre- and post-

intervention

Defining stent struts readily

Tissue prolapse between stent struts immediately

(97.5%)

Tissue characterization of plaque before and after

stent placement

Intrastent dissection (86.3%)

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3-point classification defines stent strutapposition.

Embedded ----- the leading edge is buriedwithin the intima by more than one-half itsthickness

Protrusion --- stent strut is apposed but notembedded

Malapposed ---- there is no intimal contact

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Primary imaging modalities for follow-up evaluation of several bioabsorbable vascular scaffolds (BVS), which are being studied in clinical trials (ABSORB)

OCT has been increasingly used as an endpoint in clinical trials of newer generation DES (LEADERS)

OCT helps to predict no reflow post-PCI, based on the presence of TCFA

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SAFETY

The relatively low energy used in OCT (5.0–8.0 mW)

does not cause functional or structural damage to the

coronary tissue.

Use of a contrast bolus in coronary preparation is a

concern but studies have shown that no patients

suffered contrast-induced nephropathy,

Small risk of coronary spasm and electrocardiogram

(ECG) changes during contrast administration.

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LIMITATIONS

Need to displace blood or dilute the hematocrit, either withsaline or contrast flush injection, or a combination of the two.

Shallow image penetration of 1 to 2.5 mm. This preventsassessments of cross-sectional plaque area ---- OCT has onlya limited role in the assessment of left main stem andSaphenous vein graft atherosclerosis severity.

The differentiation of calcific areas from lipid pools can beproblematic . both result in a low attenuation signal.

Imaging of Left main ostium

Imaging in patients with decreased creatinine clearance

Image artifacts

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The 2011(ACCF)/(AHA)/ (SCAI)

guidelines for PCI

1) IVUS for the evaluation of angiographically indeterminate left main lesions and angiographically indeterminate (50–70 % stenosis) non-left main coronary lesions (Class IIa LOE B)

2) IVUS to evaluate the aetiology of stent restenosis and stent thrombosis (Class IIa, Level of Evidence C).

3)The routine use of IVUS for evaluation of lesions when PCI is not planned was given a Class III recommendation

4) Currently neither the American nor European (ESC) guidelines provide recommendations for the routine use of OCT in clinical practice

5) More recent guidelines published in February 2014 by NICE suggest that the evidence on the safety of OCT to guide PCI showed no major concerns

IVUS reveals need of postdilatation

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CONCLUSION IVUS and OCT - useful image guiding tools during stent

implantation.

Intracoronary imaging may prove to be useful in reducing

complications by 1) improving the techniques of stent sizing and

placement, 2) identifying the role of necrotic-core plaque as a cause

of stent complications, and 3) assessing stent coverage and

thrombosis.

OCT - higher resolution and adds more information particularly

distinguishing thrombus formation, coronary dissection and

incomplete stent apposition following implantation.But not clear

whether this additional information helps to improve patient outcome

At present, IVUS remains the more trusted and validated imaging

modality and is the first-choice modality to guide optimal stent

implantation.

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Thank you !!!

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A bend in a mechanical IVUS

catheter due to severely

angulated lesions may cause

unnecessary friction and

generate Non-Uniform

Rotational Distortion

(NURD), which results in a

smeared image

Ring-down artifact -- Caused by

transducer oscillation filling the

area immediately adjacent to the

catheter with noise, making this

area unavailable for imaging. Seen

as bright halo of variable thickness

surrounding the catheter.

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Residual blood “sunflower” effect or“merry-go-round” effect .

Saturation Artifact

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Bubble Artifact

Fold-over Artifacts

Sew-up Artifacts

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coronary imaging

Healthcare

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