This document discusses the use of intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for assessing coronary artery disease and optimizing percutaneous coronary intervention (PCI). Some key points: 1) IVUS has better tissue penetration than OCT but lower resolution. OCT has much higher resolution which allows more accurate lumen measurement. 2) Both IVUS and OCT can help optimize stent implantation by informing lesion preparation, stent sizing and placement to minimize geographic miss and under expansion. 3) Post-PCI, a minimum stent area (MSA) below 5mm2 seen on IVUS/OCT is associated with higher risk of restenosis and stent thrombosis. Under expansion is still common.

1. IVUS vs OCT for CORONARY
REVASCULARIZATION

2. • Coronary angiography (CAG) remains the gold standard for invasive assessment of coronary artery disease (CAD) and for
guiding percutaneous coronary intervention (PCI).
• However, it is limited by
• its poor resolution,
• Angle dependency,
• vessel overlap
• foreshortening,
• significant inter- and intra-observer variability in assessing coronary stenoses.
• Further, CAG is a two-dimensional luminogram and does not provide adequate information about the vessel wall and
plaque characteristics.
• With their ability to produce high-quality cross-sectional images of the coronary arteries and tissue characterization
capabilities, Intravascular imaging (IVI) modalities compliment CAG in the qualitative and quantitative assessment of
CAD
Subban V, Raffel OC, Vasu N, Victor SM, Sankardas MA. Intravascular ultrasound and optical coherence tomography for the assessment of coronary
artery disease and percutaneous coronary intervention optimization: The basics. Indian Heart J Interv 2018;1:71-94.

3. • These imaging modalities help interventionalists optimize stent implantation in multiple ways:
1) informing the necessity for lesion preparation ;
2) directing appropriate stent sizing to maximize the final stent area ;
3) selecting the optimal stent length to cover residual disease adjacent to the lesion, thus minimizing geographic miss (GM) ;
4) guiding optimal stent expansion;
5) identifying acute complications (e.g., Edge dissection, stent malapposition, tissue protrusion); and
6) clarifying the mechanism of late stent failure (e.g., stent thrombosis, neointimal hyperplasia, stent under expansion, stent
fracture, neoatherosclerosis) .
• There are four major IVI modalities currently available for coronary imaging, namely,
• intravascular ultrasound (IVUS),
• optical coherence tomography (OCT),
• angioscopy, and
• near-infrared spectroscopy (NIRS).

4. Peter Nguyen & Arnold Seto (2020): Contemporary practices using intravascular imaging guidance with IVUS or OCT to optimize percutaneous coronary intervention,
Expert Review of Cardiovascular Therapy, DOI: 10.1080/14779072.2020.1732207

5. Equipment and Principles of Imaging
Intravascular ultrasound
• IVUS works by the same principle as with any other ultrasound. There are two basic IVUS catheter designs: mechanical/ rotational
and solid state-based imaging modality.
• The mechanical catheters (OptiCross IVUS catheter, Boston Scientific) consist of a single transducer element located at the tip of a
flexible drive cable housed in a protective sheath and operated by an external motor drive unit. The drive cable rotates the transducer
around the circumference (1800 rpm) and the transducer sends and receives the ultrasound signals at 1° increment to form the cross-
sectional image. The imaging catheters operate at a central frequency of 40 MHz or 60 MHz and are 5F or 6F compatible
• In the solid-state catheter design (Eagle Eye Catheter, Volcano), no rotating components are present. There are 64 transducer
elements mounted circumferentially around the tip of the catheter. The transducer elements are sequentially activated with different
time delays to produce an ultrasound beam that sweeps around the vessel circumference. The catheter works at a central frequency of
20 MHz and is 5F compatible

6. Mechanical catheters (OptiCross IVUS catheter) Solid-state catheter design (Eagle Eye Catheter)
The higher central frequency with mechanical system offers
better resolution and high-quality images aiding clinical
decision-making.
The longer monorail segment provides better trackability to
the solid-state catheter in complex coronary anatomy.
the central location of the guidewire port eliminates the
guidewire artifact
the transducer is house at 25 mm from the tip, which makes it
unsuitable for CTO imaging
the shorter distance from the catheter tip to the transducer (10
mm in Eagle Eye Platinum and 2.5 mm in Eagle Eye
Platinum ST IVUS Catheter; Volcano) offers advantage in
chronic total occlusion (CTO) intervention.
the outer sheath allows precise and controlled
pullback for length and volume assessment.
the catheter does not have outer sheath so that no air trapping
is present around the catheter and it does not need saline
flushing.
hindrance to the rotation of the transducer produces NURD,
and the air trapping in the sheath distorts the image quality
and needs frequent saline flushing
No rotating elements are present in the catheter and hence
nonuniform rotational deformity (NURD) does
not occur with solid-state catheter system.

7. Optical coherence tomography
• OCT is an optical analog of IVUS and uses near-infrared light to produce high-resolution cross-
sectional images of the coronary artery.
• The very high frequency of the light provides 10–15 μ resolution but at the same time limits tissue
penetration to 1–2 mm.

8. IVUS v/s OCT
• There are several key differences between OCT and IVUS
• OCT has 10 times higher axial resolution than IVUS
• OCT has limited soft tissue penetration (1 to 2 mm) compared with IVUS (5 to 6 mm),
• IVUS uses ultrasound (w40-mm wavelength at 40 MHz), whereas OCT uses infrared light (1.3-mm wavelength),
which confers significantly greater resolution
• Because the wavelength of OCT is shorter than the 8-mm diameter of a red blood cell, backscattering from blood
occurs with OCT such that the vessel wall cannot be seen without blood clearance. The combination of better
resolution and clearance of blood during OCT imaging provides a much clearer interface between lumen and plaque
surface, enabling accurate automatic lumen measurements, whereas with IVUS human interaction is required to
accurately identify lumen contours.
• Because of its superior resolution, the reproducibility of OCT measurements is better than IVUS Conversely, one of the
most useful features of IVUS that is lacking with OCT is full-thickness visibility of the vessel wall

9. Peter Nguyen & Arnold Seto (2020): Contemporary practices using intravascular imaging guidance with IVUS or OCT to optimize percutaneous coronary intervention,
Expert Review of Cardiovascular Therapy, DOI: 10.1080/14779072.2020.1732207

10. Maehara A, Matsumura M, Ali ZA, Mintz GS, Stone GW. IVUS-Guided Versus OCT-Guided Coronary Stent Implantation: A Critical Appraisal. JACC Cardiovasc
Imaging. 2017 Dec;10(12):1487-1503. doi: 10.1016/j.jcmg.2017.09.008. PMID: 29216976.

12. • Most experts believe that OCT more accurately measures lumen dimensions than IVUS
• An in vitro study by Kubo et al. reported that the OCT area was like that of a phantom model (phantom = 7.45 mm2; OCT = 7.45 0.17
mm2), whereas IVUS overestimated the area by 7.8% (8.03 0.58 mm2). In 100 lesions studied with both OCT and IVUS (in vivo), IVUS
lumen area was larger than OCT (mean difference = 0.41 mm2, 12.5%).
Kubo T, Akasaka T, Shite J, Suzuki T, Uemura S, Yu B, Kozuma K, Kitabata H, Shinke T, Habara M, Saito Y, Hou J, Suzuki N, Zhang S. OCT compared with IVUS in
a coronary lesion assessment: the OPUS-CLASS study. JACC Cardiovasc Imaging. 2013 Oct;6(10):1095-1104. doi: 10.1016/j.jcmg.2013.04.014. Epub 2013 Sep 4.
PMID: 24011777.

13. • Compared to IVUS or angiography guidance, OCT guidance PCI requires 17 to 70 ml more contrast in order to clear the
blood from the lumen.
• Because of the requirement for blood clearance, inability to visualize the aorto-ostial junction (including ostial lesions that
have a high prevalence of restenosis) is a significant limitation of OCT.

16. PRE-INTERVENTION EVALUATION OF PLAQUE TYPE RELATED TO
ACUTE STENT OUTCOMES
• LIPIDIC PLAQUE AND DISTAL EMBOLIZATION.
• Baseline IVUS or OCT may predict distal embolization and subsequent periprocedural myocardial infarction (MI) after PCI
in native arteries and re-stenotic lesions
• Morphological predictors of periprocedural MI in observational studies are
1. attenuated plaque (indicating a large necrotic core) or
2. plaque rupture by IVUS,
3. necrotic core by virtual histology IVUS, and
4. thin-cap fibroatheroma or plaque rupture by OCT.
• In a large IVUS study of 336 patients with acute coronary syndrome (ACS) and 351 patients with stable coronary artery disease,
the prevalence of attenuated plaque was 43.8% and 27.9%, respectively, and its adjusted odds ratio (OR) to predict post-PCI
TIMI<3 was 5.9 (95% confidence interval [CI]: 2.4 to 14.5) and 6.6 (95% CI: 1.4 to 32.1), respectively.
Kimura S, Kakuta T, Yonetsu T, et al. Clinical significance of echo signal attenuation on intravascular ultrasound in patients with coronary artery disease. Circ
Cardiovasc Interv. 2009;2(5):444-454. doi:10.1161/CIRCINTERVENTIONS.108.821124

19. • The sensitivity of calcium detection by IVUS relative to pathology has been reported as 89% to 90%, with specificity of
97% to 100%.1
• OCT can penetrate calcium so that its thickness and area are often evaluable, whereas IVUS is unable to analyze calcium
thickness or area because ultrasound is almost entirely reflected from the calcium surface
• Using OCT Kobayashi et al. reported that calcium area and angle were related to poor stent expansion. Thus, the presence
of angiographically visible calcium or an IVUS or OCT calcium angle >180 that is >0.5 mm thick by OCT is associated
with poor stent expansion and should prompt consideration for pre-stent adjunctive calcium modification.2
1. Friedrich GJ, Moes NY, Mühlberger VA, et al. Detection of intralesional calcium by intracoronary ultrasound depends on the histologic pattern. Am Heart J.
1994;128(3):435-441. doi:10.1016/0002-8703(94)90614-9
2. Kobayashi Y, Okura H, Kume T, Yamada R, Kobayashi Y, Fukuhara K, Koyama T, Nezuo S, Neishi Y, Hayashida A, Kawamoto T, Yoshida K. Impact of target lesion
coronary calcification on stent expansion. Circ J. 2014;78(9):2209-14. doi: 10.1253/circj.cj-14-0108. Epub 2014 Jul 14. PMID: 25017740.

20. STENT SIZING BY IVUS
• IVUS-guided stent or post-stent balloon sizing recommendations have been based on either:
1) external elastic lamina (EEL) diameters of the proximal reference, distal reference, or lesion site, usually rounded
down by (at least) 0.5 mm; or
2) Reference lumen diameters.
• Both are typically larger than angiographic reference lumen diameter measures, especially in smaller vessels.
• Although the IVUS minimum lumen area (MLA) was the parameter that best correlated with ischemia, reported thresholds
of IVUS MLA cut-offs ranged from 2.1 to 4.4 mm2, the thresholds were smaller in Asian studies than in Western studies,
and the "most common" cut-off was approximately 3.0 mm2
• Although IVUS versus FFR reports in Korean patients suggest that 4.8 mm2 is a better MLA cut-off than 6.0 mm2 in
LMCA lesions, the worst outcomes in Western patients were associated with an IVUS MLA of 5.0-6.0 mm2
Park SJ, Ahn JM, Kang SJ, et al. Intravascular ultrasound-derived minimal lumen area criteria for functionally significant left main coronary artery stenosis. JACC
Cardiovasc Interv 2014;7:868-74

21. • In patients with isolated ostial and shaft intermediate LMCA stenosis, an IVUS-derived MLA of ≤4.5 mm(2) is a useful
index of an FFR of ≤0.80.
Park SJ, Ahn JM, Kang SJ, et al. Intravascular ultrasound-derived minimal lumen area criteria for functionally significant left main coronary
artery stenosis. JACC Cardiovasc Interv. 2014;7(8):868-874. doi:10.1016/j.jcin.2014.02.015
Kang SJ, Lee JY, Ahn JM, et al. Validation of intravascular ultrasound-derived parameters with fractional flow reserve for assessment of coronary stenosis severity. Circ
Cardiovasc Interv. 2011;4(1):65-71. doi:10.1161/CIRCINTERVENTIONS.110.959148

23. STENT SIZING BY OCT
• Stent sizing based on EEL measures will usually result in larger-diameter stents being selected than sizing based on
reference measures.
• The ILUMIEN III study thus pre-specified a novel OCT-guided stent optimization algorithm to overcome the fact that OCT
often cannot visualize the EEL at the lesion site. In this trial OCT guided PCI was non-inferior to IVUS/angiographic
guided PCI.
• Stent sizing was based on the proximal and distal reference segment EEL measurements, the stent diameter was chosen by
the smaller EEL diameter of the proximal or distal reference and rounded down to the nearest 0.25-mm stent diameter.
• If the operator could not see EEL circumference >180, stent size was based on 100% of lumen diameter.
• The stent segment was divided into proximal and distal halves, and on the post-PCI OCT the MSA of each half was
compared to the respective reference lumen area; >95% was considered optimal and >90% was considered acceptable stent
expansion.
Ali ZA, Maehara A, Généreux P, et al. Optical coherence tomography compared with intravascular ultrasound and with angiography to guide coronary stent
implantation (ILUMIEN III: OPTIMIZE PCI): a randomised controlled trial. Lancet. 2016;388(10060):2618-2628. doi:10.1016/S0140-6736(16)31922-5

25. Lee CH, Hur SH. Optimization of Percutaneous Coronary Intervention Using Optical Coherence Tomography. Korean Circ J. 2019;49(9):771-793.
doi:10.4070/kcj.2019.0198

26. POST-INTERVENTION PREDICTORS OF CLINICAL OUTCOMES
UNDEREXPANSION AND THE MSA
• The most consistent and strongest parameter to predict both restenosis and stent thrombosis is the post-PCI MSA , and
MSA has been used as a surrogate of clinical outcomes in previous studies
Maehara A, Matsumura M, Ali ZA, Mintz GS, Stone GW. IVUS-Guided Versus OCT-Guided Coronary Stent Implantation: A Critical Appraisal. JACC Cardiovasc
Imaging. 2017 Dec;10(12):1487-1503. doi: 10.1016/j.jcmg.2017.09.008. PMID: 29216976.

27. • A larger MSA is still associated with less coronary artery restenosis until a plateau is reached at an MSA of ≥8
mm2.
• Soeda et al. reported OCT-MSA was found to be an independent predictor of device-oriented clinical
endpoints and TLR, with an MSA cutoff value of 5.0 mm2 for DES and 5.6 mm2 for bare metal stents.
• In ILUMIEN III, in which patients were randomized to OCT-guided, IVUS-guided, or angiography-guided
stenting, OCT MSA <5.0 mm2 was found in about one-third of patients (28.6% in the OCT arm and 31.1% in
the IVUS arm), emphasizing that a small stent area and/or under expansion is not infrequent even in
contemporary practice.
Soeda T, Uemura S, Park SJ, et al. Incidence and clinical significance of poststent optical coherence tomography findings: one-year follow up study from a multicenter
registry. Circulation 2015;132:1020–9.

28. GEOGRAPHICAL MISS AND PREDICTORS OF STENT EDGE
RESTENOSIS
• Mintz et al. 1 reported that only 7% (60 of 884) of angiographically normal-appearing coronary artery segments were normal by
IVUS. The plaque burden corresponding to the angiographically normal coronary artery segments was 51 ±13%.
• longitudinal GM is defined as an angiographic injured or diseased segment not covered by a stent, and axial GM as balloon/artery
size ratio <0.9 or >1.3.
• GM has been associated with restenosis and stent thrombosis. In the ADAPT-DES 2 study, greater stent expansion at the stent edge
and the presence of a greater stent edge plaque burden or amount of calcium or attenuated plaque were associated with edge
dissections
• In turn, an untreated edge dissection was associated with TLR, especially if the lumen area within the dissection was <5.0 mm2, the
dissection length was >3 mm, and the dissection flap radial extent was >60°.
1. Mintz GS, Popma JJ, Pichard AD, et al. Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary
angiography in 1155 lesions. Circulation. 1995;91(7):1959-1965. doi:10.1161/01.cir.91.7.1959
2. Maehara A, Mintz GS, Witzenbichler B, et al. Relationship Between Intravascular Ultrasound Guidance and Clinical Outcomes After Drug-Eluting Stents. Circ
Cardiovasc Interv. 2018;11(11):e006243. doi:10.1161/CIRCINTERVENTIONS.117.006243

29. • In the combined post-procedural IVUS data from the TAXUS IV, TAXUS V, and TAXUS VI trials (n = 531), only edge
plaque burden was a predictor of edge restenosis with a similar cutoff value of plaque burden in bare metal stents (47.1%)
and PES (47.7%).
• Using OCT, Prati et al.1 reported that residual distal edge dissection >200 mm in width and residual reference stenosis with
minimum lumen area <4.5 mm2 were associated with MACE
Liu J, Maehara A, Mintz GS, et al. An integrated TAXUS IV, V, and VI intravascular ultrasound analysis of the predictors of edge restenosis after bare metal or
paclitaxel-eluting stents. Am J Cardiol. 2009;103(4):501-506. doi:10.1016/j.amjcard.2008.10.010
1. Prati F, Romagnoli E, Burzotta F, et al. Clinical Impact of OCT Findings During PCI: The CLI-OPCI II Study. JACC Cardiovasc Imaging. 2015;8(11):1297-1305.
doi:10.1016/j.jcmg.2015.08.013

30. TISSUE PROTRUSION WITHIN THE STENT
• By IVUS, tissue protrusion through stent struts has been found in 17% to 31% of patients with stable coronary
artery disease and 46% to 69% of patients with ACS.
• by OCT, irregular tissue protrusion (presumably lipidic plaque or thrombus) has been associated with target
vessel failure (TVF).
• In an IVUS substudy of HORIZONS-AMI (Harmonizing Outcomes with Revascularization and Stents in
Acute Myocardial Infarction), which included 401 ST-segment elevation MI patients with post-stent IVUS
after primary PCI, tissue protrusion was found in 74% of patients. When the tissue protrusion was large
resulting in a small residual lumen area, it was associated with early stent thrombosis.
Soeda T, Uemura S, Park SJ, et al. Incidence and clinical significance of poststent optical coherence tomography findings: one-year follow up study from a multicenter
registry. Circulation 2015;132:1020–9.

31. ACUTE MALAPPOSITION
• Acute malapposition was detected by OCT more than twice as frequently as with IVUS: 14% versus 39% in study and
19.3% versus 38.5% in ILUMIEN III trial.

34. IVUS-GUIDED PCI TO IMPROVE OUTCOMES

35. • Meta-analyses of 8 trials (3,276 patients, 1,635 IVUS-guided and 1,641 angiography-guided; with a mean follow-up 1.4 ±
0.5 years.) demonstrates a significant reduction in MACE, TVR, and TLR with IVUS-guided DES implantation in complex
coronary lesions.
Bavishi C, G. Stone, et al. Intravascular ultrasound–guided vs angiography-guided drug-eluting stent implantation in complex coronary lesions: Meta-analysis of
randomized trials. AHJ, 2017, Vol. 185, pp.26-34.

36. OCT-GUIDED PCI TO IMPROVE OUTCOMES

37. OCT-GUIDED VERSUS IVUS-GUIDED PCI
• Thus, considering the
results of OPINION and
ILUMIEN III, an OCT-
guided PCI strategy appears
to be noninferior compared
to IVUS for both acute and
long-term outcomes.

38. OCT VERSUS IVUS FINDINGS AND PCI
GUIDANCE IN CASES OF STENT FAILURE
• Intravascular imaging is most useful in patients with stent failure (restenosis or thrombosis) to determine the mechanism and choose
the appropriate treatment.
• In a study of 298 ISR lesions evaluated by IVUS, stent underexpansion (MSA <5 mm2) was more frequent in DES (32%) than in
bare metal stents (22%).1
• OCT based study evaluating 171 second-generation DES restenosis , showed that stent underexpansion (MSA <4 mm2 and
neointimal hyperplasia <50% of stent area) was seen in 40% of ISR cases occurring within 1 year.2
• In addition, neointimal calcification was found in 20% of ISR cases occurring >1 year after implantation. identification of neointimal
calcification within an old stent is difficult by angiography and may be challenging by IVUS because of radiopacity of the old stent,
calcification behind stents, and neointimal calcification, OCT to recognize neointimal calcium may be useful to determine the
optimal treatment strategy.
1. Goto K, Zhao Z, Matsumura M, et al. Mechanisms and Patterns of Intravascular Ultrasound In-Stent Restenosis Among Bare Metal Stents and First- and Second-
Generation Drug-Eluting Stents. Am J Cardiol. 2015;116(9):1351-1357. doi:10.1016/j.amjcard.2015.07.058
2. Song L, Mintz GS, Yin D, et al. Characteristics of early versus late in-stent restenosis in second-generation drug-eluting stents: an optical coherence tomography
study. EuroIntervention. 2017;13(3):294-302. doi:10.4244/EIJ-D-16-00787

39. • As a separate phenomenon compared to acute malapposition, late-acquired stent malapposition is the result of either positive
vessel remodeling and/or thrombus resolution behind the stent struts.
• In a metanalysis by Hassan AK et al. they showed that there was an increase of very late stent thrombosis in cases with late stent
malapposition (OR: 6.5; 95% CI: 1.3 to 34.9; p = 0.02) versus those without late stent malapposition.
• In cases where angiography suggests late acquired stent malapposition (persistent staining, aneurysmal change), IVUS is
recommended because evaluation of the entire vessel wall is possible only by IVUS.
• Conversely, OCT is superior to IVUS for the identification of neo-atherosclerosis (a common cause of very late stent restenosis or
very late stent thrombosis)
• One of the potential mechanisms of stent thrombosis is uncovered stent struts . Compared to IVUS, OCT can evaluate completeness
of tissue coverage of stent struts, typically defined as visible smooth tissue on the top of the stent strut.
Hassan AK, Bergheanu SC, Stijnen T, et al. Late stent malapposition risk is higher after drug-eluting stent compared with bare-metal stent implantation and associates
with late stent thrombosis. Eur Heart J. 2010;31(10):1172-1180. doi:10.1093/eurheartj/ehn553

40. • Stent strut coverage is an important predictor of ST following DES implantation. OCT with its high-resolution better suits
for evaluation of strut coverage
• Stent strut coverage is classified into four types on OCT imaging:
1. covered-embedded: struts that are covered by tissue and not disturbing the lumen contour;
2. Covered protruding: struts that are covered but extending into the lumen disturbing the lumen contour
3. Uncovered apposed: struts that are not covered but in contact with the vessel wall;
4. uncovered-malapposed: struts that are neither covered nor in contact with the vessel wall

41. • The homogenous pattern is characterized by high backscattering and low attenuating tissue with no focal variation
• The layered pattern consists of a high backscatter adluminal layer and a low backscattering abluminal layer
• The heterogeneous pattern is made up of tissue with nonuniform optical properties with areas of high and low backscatter
throughout

45. Peter Nguyen & Arnold Seto (2020): Contemporary practices using intravascular imaging guidance with IVUS or OCT to optimize percutaneous
coronary intervention, Expert Review of Cardiovascular Therapy, DOI: 10.1080/14779072.2020.1732207

46. THANK YOU