Beyond CAG- IVUS and FFR
Dr Frijo Jose A
CAG
– Extensively used
– Entire cor anatomy,
including small & distal
vessels
– Helpful in clinical
decision making
1. Eccentricity
2. Vascular remodelling
3. Relative % stenosis
4. Reference segment
assessment
5. Limited correlation
with physiology
6. Post PTCA/dissec
1. Eccentricity of lesions
• In coronaries with atherosclerosis, the lumen
is often irregular and non-circular
Schematic representation of an important limitation of projection imaging
Topol, E. J. et al. Circulation 1995;92:2333-2342
Pitfall: lesion eccentricity
Pitfall: lesion eccentricity
Angiographically unrecognized left main coronary artery disease
Topol, E. J. et al. Circulation 1995;92:2333-2342
2. Vascular
Remodelling
(Glagov’s phenomenon)
Effect of coronary remodeling
Topol, E. J. et al. Circulation 1995;92:2333-2342
• These plaques are
particularly prone
to rupture.
• Missed by
angiography.
3. Reference seg assessment & Relative % stenosis
Concealment of severe coronary disease by diffuse concentric involvement
Topol, E. J. et al. Circulation 1995;92:2333-2342
IVUS Imaging
2D Cross-Sectional
Imaging
4.Limited correlation with physiology and
pre-stenting
Chest pain with normal coronaries
50 % have plaques on IVUS, which might have ruptured
to cause the chest pain
IVUS before PCI
• Baseline plaque composition
• Vessel size
• Confirm CAG severity
• Lesions of uncertain severity- IVUS can solve- (changed
original provisional decision in 20%)
• Intermediate severity (40-75%)- FFR can provide further
information (>0.75- favorable outcome with medical Rx)
• LMCA obstruction–
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Contrast in cusps can obscure the ostium
Streaming of contrast can falsely suggest narrowing
There may not be a normal reference segment
Branch vessels overlap distal part- stenosis is masked
• In ostial lesions, IVUS provides information about whether
there is a lesion at all and whether the lesion is truly ostial
or not
Quantitation of atheroma
(slight overestimation)
• Intimal thickness ≥0.5 mm - abnormal and
indicative of atherosclerosis
• Total atheroma volume- motorized device
pulls back transducer at 0.5 mm/sec. From the
slices so obtained, TAV is found by the
Simpson’s rule
• Most plaques are eccentric- max thickness is
more than twice the minimum thickness
• Fatty streaks are not clearly identified.
• Atheroma- fibrosis and calcification are clearly
identified, but hypoechoic part may be lipid, thrombus
or necrotic degeneration. Radiofrequency analysis
superimposed on IVUS helps to clarify the situation.
• More sensitive than fluoroscopy to detect calcification.
• Positive remodeling- landmark study by Glagovinitially there is increase in plaque area without
decrease in luminal area- due to increase in EEM
(enclosed) area.
large, soft, lipid-laden atheroma with a thin fibrous cap
is seen (arrows). It is eccentric, involving only
approximately 50 percent of the vessel wall
shows a circumferential atheroma with an area
of focal calcification is evident (arrow).
• ACS– Less obstructive plaques
are much more common
– More lipid pool
– Thin fibrous cap
– Ruptured cap
– Superimposed thrombus
– Multiple sites of rupture
Potentially unstable coronary lesion
Echolucent
5. post-stenting and dissection
• Initial procedural results
• Quantifying late intimal hyperplasia
Overestimation of lumen gain by angiography after balloon angioplasty
Topol, E. J. et al. Circulation 1995;92:2333-2342
• IVUS – mechanisms of lumen gain by balloon
dilation– Fracture of the plaque
– Plaque is redistributed axially
– Arterial wall stretching
• IVUS and stenting– Pioneering report by Colombo
– High chance of incomplete stent apposition with
usual dilation- not seen by check CAG - contrast
flows outside the porous stent - fills space
provided by the vessel which has been passively
dilated by the balloon dilation. Higher pressure
dilation or larger balloon size solves problem
– Even aft high pressure dilation, when IVUS was
done, additional procedures done in 20- 40 %
– STARS study- decreased restenosis in IVUS guided stenting.
TULIP study- decreased restenosis only in long and diffuse
lesions.
– Stent to reference area ratio does not predict TVR. Stent
area of 9 mm2 or more predicts freedom from restenosis.
– Very useful in suspected dissection after stenting- to know
the full length of the dissection.
– Useful to discern the cause of “persistent haziness” after
stenting.
– Restenosis mech- usually neo-intimal proliferation. Also,
restenosis at the margins. No decrease in the stent areastents can withstand remodeling.
• Late stent malapposition
IVUS
– Tomographic views
– Vessel wall + lumen
visualization
– Validated quantitative
software
– Plaque characterization
– Need to instrument vessels
– Limited to proximal
segments
– Bifurcation lesions
– Cost
– Not as well validated for
clinical decision making
– Limited correlation with
physiology
– Not always perpendicular to
vessel axis
IVUS Pitfall:
Imaging plane not perpendicular to vessel axis
ACC/AHA Recommendations for Coronary IVUS
Class II A
• 1. Evaluation of lesion severity at a location
difficult to image by angiography in patients
with a positive functional study and a
suspected flow-limiting stenosis
• 2. Assessment of a suboptimal angiographic
result after coronary intervention
• 3. Diagnostic and management of coronary
disease after cardiac transplantation
Absolute flow reserve
– Drugs- intracoronary papaverine, intracoronary
adenosine, intravenous dipyridamole
– Ratio of maximum to resting flow rate
– Below 2- causes stress induced ischemia
– Reduction may be due to ↑resting flow also
– ↓ in severe stenosis and microcirculatory abn
Relative flow reserve
– Maximum exercise/pharmacological dilation
– Minimum threshold of 0.8
– Inaccurate in multivessel disease
– Inaccurate in microcirculatory disease
Fractional flow reserve
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During maximum vasodilation
Mean cor pressure/mean Ao pressure
Unaffected by alteration in resting flow
Can immediately assess importance of a lesion for
guiding intervention
Considerable prognostic information
FFR more than 0.75- excellent outcome with deferred
rather than prophylactic intervention
Affected by microcirculatory disease
Most direct way to assess physiological significance of
a lesion
Simultaneous measurement of pressure in aorta and distal LAD at rest
Simultaneous measurement of pressure in aorta and distal LAD
following intracoronary adenosine
Clinical uses of FFR
1. Determining the hemodynamic significance
of CAG intermediate lesions:
• Pijls et al - cutoff 0.75 detected ischemia –
sensitivity- 88%, specificity- 100%, diagnostic
accuracy- 93%
• DEFER - moderate CAD + FFR>0.75 - PCI v/s
medical – PCI event rate > medical event rate
Clinical uses of FFR
2. Determining success of PCI:
• Multicenter registry - FFR determined
immediately after stenting – most signi
independent variable related to future events
Clinical uses of FFR
3. Determining significance of LMCA lesions:
• Bech et al- 54pts (29/12)- equivocal LMCA
• Medical - 24 pts with FFRs >0.75
• CABG - 30 pts with FFR <0.75
• Survival – medical- 100%, CABG- 97%
Clinical uses of FFR
4. Determining the significance of multiple
stenoses in the same coronary artery:
• FFR can be used to “map” the hemodynamic
effects of multiple stenoses in the same vessel
• FAME (1005pts)- clinical outcomes after PCI
on CAG v/s CAG+ FFR in multivessel disease
• FFR gp- 37% of PCI indented lesns- FFR >0.80
• 1 yr- composite event rate -18.3% CAG-guided
gp V/S 13.2% CAG+FFR-guided group
Recommendations for Use of
Fractional Flow Reserve
Class IIa
• Can be useful to determine whether PCI of a
specific cor lesion is warranted
• Can be useful as an alternative to performing
noninvasive functional testing (eg, when the
functional study is absent or ambiguous) to
determine whether an intervention is warranted
• In the assessment of the effects of intermediate
cor stenoses (30% to 70% luminal narrowing) in
pts with anginal symptoms
Case study
Case study
Case study
Case study
Case study