Coronary lesion assessment

Coronary Lesion Assessment
Dr Uday Prashant

Lesion Assessment – Qualitative &
Quantitative
• Coronary Angiogram
a) Eyeballing
b) QCA
• CT angiogram
• IVUS
• OCT
• FFR

Significant stenosis
Stenosis which is > 50 % diameter of vessel
or
Which is > 70 % area of vessel
or
Which causes pressure drop across the lesion.
The resistance of vessel is inversely related to 4 th power of diameter of
vessel and directly related to length of vessel
R α K L/D4
Very long lesions even if max diameter is <50% can sometimes be
hemodynamically significant (physiological or functional significance
of lesion)

Visual Assessment
• Visual assessment methods tend to underestimate
<50% stenosis and overestimate > 50% stenosis.
(Flemming Et al)
• Humans are basically biased individuals similar to
EF estimation by eyeballing .
• Cannot be used for studies, borderline lesions
eccentric lesions and complex plaques.
• Adv :- Easiest, quickest but lot of errors.

Angiogram-Interpretation
 A systematic interpretation of a coronary angiogram would involve:
 Evaluation of the extent and severity of coronary calcification just prior to
or soon after contrast opacification
 Lesion quantification in at least 2 orthogonal views:
 Severity
 Calcification
 Presence of ulceration/thrombus
 Degree of tortuosity
 ACC/AHA lesion classification
 Reference vessel size
 Distal vessels (graftable or not)
 Bifurcation/trifurcation stenosis
 Grading TIMI myocardial perfusion blush grade
 Identifying and quantifying coronary collaterals

Lesion Length
• Lesion length > 20 mm called diffuse.
Methods used to measure lesion length are
“shoulder-to-shoulder” method vessel narrowed
>20%, or
Lesion length with >50% narrowing
Distance between proximal and distal
“angiographically” normal segements
“Tandem Lesion” If the gap between lesions < 3 *
reference diameter of vessel called Tandem lesion
and considered one lesion

Ostial & Angulated
• Ostial lesions defined as those arising within 3
mm of origin of vessel or branch
• 2 types aorto-ostial & non aorto-ostial
(bifurcation)
• Aorto – ostial lesions are fibrocalcific, require
atherctomies and while positioning stent <
1mm stent should be in aorta.
• Angulation measured at site of maximum
stenosis

Various abnormal lesions and their descriptions

Lesion Classification: Coronary Angiographic Outcomes Predictors
Based on AHA/ACC Grading System

Left main thrombotic occlusion and
case of RCA spontaneous dissection

Cornary ectasia is >50% of length of vessel dilated
whereas Coronary aneurysm is localised dilatation of
artery atleast >1.5 times reference diameter

• At the time of the trial design (in 2003-
2004), a retrospective website survey of
104 medical centers over a period of 3
months showed that 12,072 patients (1/3
LM, 2/3 3VD) were revascularized by
surgery (2/3) or by PCI (1/3).
• The SYNTAX randomized trial is an
attempt to provide an evidence-base to
determine whether PCI versus surgery is
better.
SYNTAX score
Kappetein et al, Eur J Cardiothorac Surg. 2006;29:486-491

Patient Profiling
Local Heart team (surgeon
& interventional
cardiologist) assessed
each patient in
regards to :
• Patient’s operative risk (EuroSCORE &
Parsonnet score)
• Coronary lesion complexity (Newly
developed SYNTAX score)
• Goal: SYNTAX score to provide
guidance on optimal
revascularization strategies for
patients with high risk lesions
Sianos et al, EuroIntervention 2005;1:219-227
Valgimigli et al, Am J Cardiol 2007;99:1072-1081
Serruys et al, EuroIntervention 2007;3:450-459
BARI classification of coronary segments
Leaman score, Circ 1981;63:285-299
Lesions classification ACC/AHA , Circ 2001;103:3019-3041
Bifurcation classification, CCI 2000;49:274-283
CTO classification, J Am Coll Cardiol 1997;30:649-656
No. &
Location
of lesion Left
Main
Tortuosity
3 Vessel
Thrombus
Bifurcation
CTO
Calcification
SYNTAX
SCORE
Dominance

Angulation in Bifurcation Stenosis

Medina Bifurcation classification

SYNTAX Scores
• Low scores :- 0 – 22 ; PCI & CABG results same
• Intermediate scores :- 23 – 32 CABG results
better in long term.
• High score :- > 33; CABG better than PCI.

Quantitative Coronary Angiogram
• 2 Dimensional & 3 Dimensional.
• Earlier manually done by calipers later done through
computers.
• Invented by Greg Brown in University of Washington
30 yrs back
• Good quality angiograms at least two orthogonal views
required to avoid
foreshortening, vessel overlapping, irregular margins.
3 D imaging utilizes standard 2 D images 30` apart and
reconstructs

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0(m m )
1.0
2.0
3.0
4.0
5.0
6.0
(m m )
op d
r

TIMI Flow Grades
 TIMI 0 flow: absence of any antegrade flow beyond a coronary
occlusion
 TIMI 1 flow: (penetration without perfusion) faint antegrade coronary
flow beyond the occlusion, with incomplete filling of the distal coronary
bed
 TIMI 2 flow: (partial reperfusion) delayed or sluggish antegrade flow
with complete filling of the distal territory
 TIMI 3 flow: (complete perfusion) is normal flow which fills the distal
coronary bed completely
Gibson CM, et al. Am Heart J. 1999;137:1179–1184

TIMI Myocardial Perfusion Grades
 Grade 0: Either minimal or no ground glass appearance (“blush”) of the
myocardium in the distribution of the culprit artery
 Grade 1: Dye slowly enters but fails to exit the microvasculature. Ground glass
appearance (“blush”) of the myocardium in the distribution of the culprit lesion that
fails to clear from the microvasculature, and dye staining is present on the next
injection (approximately 30 seconds between injections)
 Grade 2: Delayed entry and exit of dye from the microvasculature. There is the
ground glass appearance (“blush”) of the myocardium that is strongly persistent at
the end of the washout phase (i.e. dye is strongly persistent after 3 cardiac cycles of
the washout phase and either does not or only minimally diminishes in intensity
during washout).
 Grade 3: Normal entry and exit of dye from the microvasculature. There is the
ground glass appearance (“blush”) of the myocardium that clears normally, and is
either gone or only mildly/moderately persistent at the end of the washout phase (i.e.
dye is gone or is mildly/moderately persistent after 3 cardiac cycles of the washout
phase and noticeably diminishes in intensity during the washout phase), similar to
that in an uninvolved artery.
Gibson CM, et al. Circulation. 2000;101:125-130

Coronary Angiography
Distal Blood Flow/Collateral Classification Based
on TIMI Trial
Collateral Supply Contrast Flow
1 Absent
2 Minimal
3 Well
developed
Adapted from TIMI

Total occlusion with collaterals

Limitations of Angiographic
assessment
• Inadequate vessel opacification. Guide not
properly engaged, streaming effect.
• Eccentric and calcified lesions – inaccurate
• Superimposition of branches.
• Microchannel recanalization :- difficult to
differentiate CTO with well developed bridging
collaterals or tightly stenotic lesion.

Assessment of coronary artery
stenosis by angiogram
• Luminogram
• Purely anatomical
• Inter and intra observer variability
• Oculostenotic reflex

IVUS Technology
• Real time high resolution imaging.
• 2D tomographic assessments of vessels
Also longitudinal and 3D computer asssited
reconstruction.
• Allows assessment of total vessel lumen and
plaque dimension in vivo.

Basic Hardware
• Regular 0.014’’ guide wire over which 2.5F to
3.5F catheters with < 1mm ultrasound
transducer at tip.
• The usg element rotates at 1800 rpm and
frequencies emitted are 40 -45 MHz.
• Always use NTG before IVUS imaging.

Two main IVUS systems are currently in use:
1- A mechanical system that contains a flexible
imaging cable which rotates a single transducer
at its tip inside an echo-lucent distal sheath.
2- An electronic solid state catheter system with
multiple imaging elements at its distal tip, providing
cross sectional imaging by sequentially activating
the imaging elements in a circular way.
• 1 is usually smaller than 2.

• Motorized pull back of transducer (0.25-1mm/sec,
usually 0.5mm/sec)
• Volumetric measurement.
• Imaging frequencies increased- improved qualitative
assessment of atherosclerotic plaques.
- Soft, low echogenecity
- Fibrous, high echogenicity
- Calcified, high echogenicity with acoustic
shadowing/ reverberations.

IVUS – Advantages.
• Atherosclerosis is diffuse inflammatory
disease and reference points are frequently
narrowed and leads to underestimation of
lesion stenosis.
• IVUS imaging measures total vessel area by
delineating external elastic membrane which
gives true vessel area. (Glagov phenomenon)

Vascular Remodelling
(Glagov’s phenomenon)

IVUS criteria for stenosis
• Significant stenosis
LMCA :- 6 mm2
Prox Vessels :- 4 mm2
Less specific for physiological significance.
FFR better.
Long term clinical outcome based on above
criteria are not known.

IVUS Imaging
2D Cross-Sectional
Imaging

IVUS
Advantages
– Tomographic views
– Vessel wall + lumen
visualization
– Excellent NPV+PPV
– Validated quantitative
software
– Plaque characterization
Disadvantages
– Need to instrument
vessels
– Limited to proximal
segments
– Cost
– Not as well validated for
clinical decision making
– Limited correlation with
physiology
– Not always perpendicular
to vessel axis

IVUS Imaging:
Plaque Surface and Volume
Longitudinal
Plane
Transverse
Plane

•More advanced IVUS plaque
characterization is possible by IVUS
1- Analysis of the backscatter IVUS radiofrequency
data provided a color coded mapping based on
the different backscatter signals among the tissue
types (virtual histology).
- Allows examination of the different plaque
components in more details (fibrous, fibro-lipidic,
calcium, lipid core)
Nair et al Circulation. 2002 Oct 22;106(17):2200-6.

FibrousSoft
Superficial Ca Deep calcification

Quantitative Coronary Ultrasound (QCU)

Evaluating Intermediate Coronary Lesions.
• Abizaid et al compared various IVUS parameters
with CFR.
• Linear relation between CFR and minimum LCSA.
• They defined minimum LCSA as ≤4mm2 and
demonstrated concordance of 89% with CFR
(abnormal CFR <2).
Am J Cardiol. 1998 Aug 15;82(4):423-8.

• Nishioka et al compared IVUS parameter with
nuclear perfusion imaging.
• They found that minimum LCSA ≤4mm2 had
sensitivity of 88% and specificity of 90% for predicting
reversible perfusion defect.
• Other IVUS parameters (eg % area stenosis)
performed less well.
J Am Coll Cardiol. 1999 Jun;33(7):1870-8

• Takagi et al compared IVUS parameters with FFR
for determining functional significance of moderate
lesions.
• Strong correlation between minimum LCSA and FFR
•Using cutoff of ≤3mm2 to define abnormal minimum
LCSA and < 0.75 to define abnormal FFR, the
investigators found IVUS had a sensitivity of 83%
and specificity of 92% for detecting ischemia
producing lesions based on FFR.
Circulation. 1999 Jul 20;100(3):250-5.

• Briguori et al compared IVUS with FFR only in
patients with intermediate lesions.
• IVUS minimum LCSA was significantly related to
FFR (r=0.41, p<0.004).
• The sensitivity and specificity of minimum IVUS
LCSA of ≤4mm2 for predicting FFR ≤0.75 were
92% and 56%.
Am J Cardiol. 2001 Jan 15;87(2):136-41.

ACC/AHA/SCAI guideline summary: Intravascular ultrasound
(IVUS) at the time of
percutaneous coronary intervention (PCI)
Class IIa –
• Following PCI with stenting, to assess the adequacy of
deployment through examination of the extent of stent
apposition and determination of the minimum luminal
diameter.
. IVUS is reasonable for the assessment of angiographically
indeterminant left main CAD.248–250
• Following diagnostic angiography to determine the
mechanism of in-stent restenosis (inadequate expansion
versus neointimal proliferation) so that appropriate therapy
(repeat balloon expansion versus brachytherapy) is selected.

• Following diagnostic angiography to evaluate a coronary
obstruction at a location difficult to image in a patient
with a suspected flow-limiting stenosis.
• Following PCI to assess a suboptimal angiographic result.
• Before PCI to establish the presence and distribution of
coronary calcium when adjunctive rotational atherectomy
is contemplated.
• Before PCI to determine plaque location and
circumferential distribution in anticipation or directional
coronary atherectomy

Class IIB
• Following diagnostic angiography which reveals no focal stenoses or
mild coronary artery disease to further evaluate the extent of
atherosclerosis in patients with characteristic anginal symptoms and
a positive functional study.
• Following diagnostic angiography to assess lesion characteristics and
vessel dimensions in the selection of an optimal revascularization
device.
• Following cardiac transplantation, to aid in the diagnosis of coronary
disease.
Class III - :
• Following diagnostic angiography when the angiographic diagnosis is
clear and no interventional treatment is planned.

OCT – Optical Coherence Topography

OCT findings of plaque morphology
• Fibrous plaques were observed as
homogenous signal-rich findings.
• Calcific plaques were recorded as echo-lucent
images with sharp borders.
• Lipid rich plaques were demonstrated as echo-
lucent images with diffuse borders

Advantages of OCT
• Lumen area and diameter could be accurately
measured by OCT as in IVUS
• OCT can identify all three layers of coronary
artery clearly than IVUS.
• Thickness of intima medial thickness can be
measured more accurately with OCT when
compared with IVUS.

• OCT could identify different tissues by the
reflections between the layer of the different
tissue components.
• OCT can identify accumulation of macrophages
within fibrous cap of vulnerable plaques as
different light reflections
• Better tissue characterization than IVUS.
• Limitation in depth of beam penetration.

FFR
• Concept of Coronary vascular resistance
R1, R2, R3.
• Autoregulation – myogenic regulation and
flow mediated dilatation.
• Absolute coronary flow reserve (CFR) is ratio
of peak flow to rest flwo

Definition
• It is ratio of driving pressure of
microcirculation flow distal to stenosis to
driving pressure proximal to stenosis in a
maximally dilated microvascular resistance
vessels (R2).
• FFR = Pd/Pa0

• First compartment consists of
large epicardial vessels which are
also referred to as ‘conductance
vessels’
• Minimal resistance to blood flow.
• Therefore, the pressure in the
distal part of a healthy coronary
artery should be equal to central
aortic pressure.
• The second compartment
consists of arteries smaller than
400 microns, or ‘resistive vessels’
• Myocardial flow is controlled
predominantly by resistive
vessels.

Fractional flow reserve
• Equivocal or intermediate lesions , and in the absence of
demonstrated ischaemia, decision making based on
angiography alone is challenging.
• FFR has been extensively described and validated as a
technique capable of identifying functionally significant lesions
• FFR value below the threshold value of 0.75 corresponds to
inducible ischaemia
• Studies have shown that a strategy of revascularization based
on FFR results in this context is acceptable.

FAME study: DESIGN
Randomized multicenter study in 1000 patients
undergoing DES-stenting for multivessel disease
in 20 US and European centers
Multivessel disease:
Stenoses of > 50% in at least 2 of the 3 major
coronary arteries
• independent core-lab
• independent data analysis
• blinded adverse event committee
FFR Cut-off: 0.80

FAME study: BACKGROUND (1)
• Stenting of non-ischemic stenoses has no benefit
compared to medical treatment only
• Stenting of ischemia-related stenoses improves
symptoms and outcome
• In multivessel coronary disease (MVD), identifying
which stenoses cause ischemia is difficult:
Non-invasive tests are often unreliable in MVD and
coronary angiography often results in both under-
or overestimation of functional stenosis severity

Is it safe ?
• 6415 coronary
angiographies, FFR was
measured in 407 (6.3%)
patients (469 lesions)
• The only FFR related
complication was an
occlusive dissection due
to a plaque dissection
by the pressure wire.

113
Use of FFR
MODIFIED
Recommendation
Coronary pressure (fractional flow reserve [FFR])
or Doppler velocimetry can be useful to
determine whether PCI of a specific coronary
lesion is warranted. FFR or Doppler velocimetry
can also be useful as an alternative to performing
noninvasive functional testing (e.g., when the
functional study is absent or ambiguous) to determine
whether an intervention is warranted.
It is reasonable to use intracoronary physiologic
measurements (coronary pressure [FFR])(Level of
Evidence: A)
or Doppler velocimetry (Level of Evidence: C)) in the
assessment of the effects of intermediate coronary
stenoses (30% to 70% luminal narrowing) in patients
with anginal symptoms.
III IIaIIaIIa IIbIIbIIb IIIIIIIIIIII IIaIIaIIa IIbIIbIIb IIIIIIIIIIII IIaIIaIIa IIbIIbIIb IIIIIIIIIIIaIIaIIa IIbIIbIIb IIIIIIIII

114
Use of FFR
MODIFIED
Recommendation
Routine assessment with intracoronary
physiologic measurements such as
coronary pressure (FFR) or Doppler
ultrasound to assess the severity of
angiographic disease in concordant
vascular distribution in patients with
angina and a positive, unequivocal
noninvasive functional study is not
recommended.

Limitations of FFR
Cannot be used in conditions of microvascular disease
because autoregulation not possible
LVH
Endothelial dsyfunction states lile hypercholesteremia.
LMCA & Graft stenosis are excluded in FAME study.
Optimal result of PCI cannot be assessed as in IVUS or OCT

FFR not reliable
• Anemia,
• Renal Failure,
• Hyperthyroid states and other hyperdynamic
circulation states.
• In collaterals

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