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%, orLesion length with >50% narrowingDistance 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

Simple Vs Complex lesions

Thrombotic lesions

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;1:219-227Valgimigli et al, Am J Cardiol 2007;99:1072-1081Serruys et al, EuroIntervention 2007;3:450-459

BARI classification of coronary segmentsLeaman score, Circ 1981;63:285-299Lesions classification ACC/AHA , Circ 2001;103:3019-3041Bifurcation classification, CCI 2000;49:274-283CTO classification, J Am Coll Cardiol 1997;30:649-656

No. &Locationof lesion Left

Main

Tortuosity

3 VesselThrombus

BifurcationCTO

Calcification

SYNTAXSCORE

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

QCA

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 Flow1 Absent2 Minimal3 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

Eccentric Lesions

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 guided stent deployment

Vulnerable Plaque

IVUS Imaging2D Cross-Sectional

Imaging

IVUSAdvantages

– 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

LongitudinalPlane

TransversePlane

•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.

FibrousFibrousSoftSoft

Superficial CaSuperficial Ca Deep calcificationDeep calcification

Echolucent

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

Comparsion of IVUS vs OCT

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

OCT versus Histology

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

Coronary resistance

• 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.

Bernoulis equation

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.

DEFER Trial

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 majorcoronary 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.

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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.

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Use of FFR

MODIFIED Recommendation

Routine assessment with intracoronaryphysiologic measurements such ascoronary pressure (FFR) or Dopplerultrasound to assess the severity ofangiographic disease in concordantvascular distribution in patients withangina and a positive, unequivocalnoninvasive functional study is notrecommended.

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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

Thank You