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Table of Contents
REVIEW ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 3  |  Page : 89-105

Current concepts of optical coherence tomography assessment of left main coronary artery during coronary interventions


Department of Cardiology, Senior Interventional Cardiologist, Sunshine Hospitals, Hyderabad, Telangana, India

Date of Submission02-Nov-2021
Date of Decision29-Dec-2021
Date of Acceptance19-May-2022
Date of Web Publication14-Sep-2022

Correspondence Address:
Dr. Sridhar Kasturi
Sunshine Heart Institute, Secunderabad, Hyderabad, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jicc.jicc_61_21

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  Abstract 


Conventional angiography is poor in assessing type of plaque, plaque volume, disease extent, severity and features associated with optimization of percutaneous coronary intervention (PCI), whereas Intra-Vascular Ultra-Sound (IVUS) and optical coherence tomography (OCT) overcome these limitations by providing cross sectional images of vessel wall, and longitudinal extent of disease. OCT provides high-resolution images at the cost of limited penetration compared with IVUS with an axial spatial resolution of 10–20 μm versus 100–200 μm, lateral resolution of 20 μm versus 200 μm, and penetration depth 1–2.5 mm versus 10 mm, respectively. OCT measurements were proved to be nearer to the actual luminal areas whereas IVUS measurements were overestimated and were less reproducible in the phantom model. OCT and IVUS are proved to be a valid guidance for optimization of PCI. However, usefulness of OCT in day to day practice is very limited in the assessment of Left Main disease. Both imaging technologies have different distinct features, these are complementary and should be opted carefully for each patient based on pros and cons, and clinical indications of each technique.

Keywords: Imaging, intra-vascular ultra-sound, left-main coronary artery, optical coherence tomography


How to cite this article:
Kasturi S. Current concepts of optical coherence tomography assessment of left main coronary artery during coronary interventions. J Indian coll cardiol 2022;12:89-105

How to cite this URL:
Kasturi S. Current concepts of optical coherence tomography assessment of left main coronary artery during coronary interventions. J Indian coll cardiol [serial online] 2022 [cited 2022 Oct 1];12:89-105. Available from: https://www.joicc.org/text.asp?2022/12/3/89/356069




  Introduction Top


Patients with left main Coronary Artery (LMCA) disease have some special features which can influence procedural planning of percutaneous coronary intervention (PCI); short vessel segment, lack of a reference segment in the presence of diffuse atheroma, frequent overlapping daughter branches, foreshortening, diameter discrepancies due to tapered anatomy, plaque eccentricity, more often associated with calcific plaques that are difficult to assess accurately by angiography. Conventionally, an angiographic cut off of more than 50% diameter stenosis (equivalent to more than 75% area stenosis) has been used to indicate clinical significance, which is based on the early work of Gould et al.,[1] in an animal model that demonstrated a reduction in hyperemic flow across LM lesions of more than 50% diameter stenosis. LM atherosclerotic plaque extension involving the proximal left anterior descending (LAD), Left Circumflex (LCX) or both may be seen in 90%, 60.4% and 62% of patients, respectively, and isolated involvement of ostium of LAD was observed in 9.3%, and LCX in 17.3% of patients with LM bifurcation lesions.[2]

Conventional angiography is poor in assessing the type of plaque, plaque volume, disease extent, severity, and features associated with suboptimal stent deployment, whereas intravascular imaging overcomes these limitations by providing cross-sectional images of vessel wall, type of plaque, and longitudinal extent of plaque distribution. Optical coherence tomography (OCT) provides high-resolution images at the cost of limited penetration compared with Intra-Vascular Ultra-Sound (IVUS) with an axial spatial resolution of 10–20 μm versus 100–200 μm, lateral resolution of 20 μm versus 200 μm, and penetration depth 1–2.5 mm versus 10 mm, respectively.[3] OCT measurements were proved to be nearer to the actual luminal areas whereas IVUS measurements were overestimated and were less reproducible in the phantom model. OPUS–CLASS study showed IVUS guidance achieved a large minimal luminal diameter and area than OCT by 9% and 10%, respectively. OCT and IVUS are proved to be a valid guidance for optimization of PCI. However, experience is very limited about the usefulness of OCT in the assessment of LM disease so far. OCT has greater sensitivity for detection of thrombus, stent under expansion, struts mal apposition and edge dissection, suggesting it might be a valuable option for LM PCI guidance. OCT has a limited penetration depth, especially in lipid rich plaque. In contrast, calcified plaque can be visualized well with OCT, whereas IVUS is not capable of penetrating calcified plaques. Therefore, IVUS should be preferred for assessing the plaque burden and vessel size in patients presenting with lipid rich plaque, whereas OCT should be preferred for calcified plaques.[4]

Rocket's study showed that overall more than 90% of the quadrants of LM were adequately assessable using OCT. It detected almost 60% more atherosclerotic plaques than angiography, and plaques were preponderantly fibrous or fibro-calcific with intimal hyperplasia, and is very useful for assessing distal LM lesions, may not be suitable for patients with ostial LM lesions, tortuous, very large, and short LMCA lesions. In the latest guidelines of the European society of cardiology and the European Association for Cardiothoracic Surgery recommended OCT as well as IVUS for procedural optimization as Class IIa.[5]

Optimal OCT imaging occurs in vessels <5 mm in diameter, while the range of LMCA diameter in 3.5–5.5 mm, and imaging acquisition may not be possible in extremely tight and unstable lesions, sometimes requires predilatations for adequate clearance of blood with contrast as near infrared light is fully attenuated by blood. IVUS scores over the OCT in imaging of patients with ostial lesions of LMCA, due to difficulty in clean out the blood from the vessel to acquire good image on the OCT, and patients with renal disease due to possible worsening renal function due to CIN.[6] Improper flushing of blood with contrast in large vessels or shadow of guide wire in OCT may lead to inaccurate assessment of mal apposition or guide wire re-crossing portion due to artifacts. OCT has limitation in identification of external elastic lamina in segments with large lipid rich plaques which might lead to smaller device selection due to lumen based approach in contrast to IVUS which can assess EEL very clearly even in lesions with large plaque burden. Imaging artefacts more often seen in the proximal LMCA and less in distal LMCA, and proximal segments of its branches. Majority artefacts were observed in the proximal Left Main (LM) (18.6%) and frequency gradually declines distally in distal LM and LM branches (mid-LM 5.8%, distal LM 3.6%, ostium of LAD 2.6%, and ostium of LCX 0%). Most artefacts are due to quadrants out of the field of view and residual blood (45.1% and 44.7%, respectively), and other commonly observed artifacts are Sew-up or seam artifacts, and elliptical cross sectional images of vessel wall due to eccentric position of imaging catheter.[7]


  Image Acquisition Top


For the assessment of ostium of LM, choosing proper guide is very important in obtaining high resolution images without or limited artefacts. Extra back-up catheters (EBU or XB) may allow proper alignment and engagement of the LM to get adequate contrast flushing for clearance of blood. However, the chances of missing ostium very high due to deep seating in short LMCA. Imaging of stent at ostium is very crucial for identifying under-expansion, malapposition, Longitudinal Stent Dislodgement (LSD), and ab-luminal location of GuideWire which are more common in the ostio-proximal segment than distal LM due to tapered anatomy in majority of patients. The Judkins Left (JL) guide can be positioned easily at the ostium but difficulty in obtaining good images due to inadequate flushing.[8]


  Optical Coherence Tomography New Algorithm– Morphology-Lesion Length-Diameter Medial Edge Dissection-Apposition-Expansion Top


The assessment of plaque morphology is helpful in planning PCI strategy, inadequately prepared calcium plaque without proper plaque modification can lead to procedure delay and increased procedure-related events. Pre stenting OCT results in procedural change in more than 50% of the cases in terms of stent length and diameter, and change in post stent optimization is reported in at least 27% of the cases.

New Algorithm is proposed by light laboratory study investigators to implement a simple work flow chart to make it simple and convenient to use while performing OCT guided interventional procedures.

Prepercutaneous coronary intervention optical coherence tomography run to strategize (morphology-lesion length-diameter)

Step 1: Assessment of morphology (plaque)

The determination of the predominant plaque morphology guides the procedural strategy before stent implantation [Figure 1] and [Figure 2]. PCI of coronaries with lipid-rich plaque lesions can be treated with direct stenting, fibrotic, and fibro-calcific plaque lesions require pre dilatation with Non-Compliance (NC) balloon, cutting, or scoring balloons [Figure 3]. Lesions with thick superficial calcium, calcific nodule (CN) require plaque modification devices such as OPN NC/ROTAblation/Orbital Atherectomy/IVL Intra-Vascular Lithotripsy (IVL)/Excimer Laser Coronary Angioplasty. OCT differentiates superficial calcium from deep calcium, assess its thickness, length and circumferential distribution [Table 1]. If superficial calcium thicknesses more than0.5 mm, length more than 5 mm, and arc more than 180°, calculate calcium expansion index [Table 2].[9] Patients with high expansion index require plaque modification prior to placing a stent otherwise it may lead to under expansion[10] of the stent which is associated with increased stent thrombosis, and In-Stent Restenosis (ISR). In patient's plaque modification, the frequency of restenosis and target lesion revascularization (TLR) was significant lower in whom calcium fractures are seen on OCT compared with those without calcium fracture [Figure 4] and [Figure 5].[11]
Figure 1: Pre-percutaneous coronary intervention optical coherence tomography run to strategize

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Figure 2: Optical coherence tomography image interpretation

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Figure 3: Plaque morphology by optical coherence tomography image interpretation

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Figure 4: Prediction of neointimal calcium in sent expansion, calcium fractures and frequency of restenosis rate and target lesion revascularization rate

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Figure 5: Post plaque modification – evidence of fractures in our cases by optical coherence tomography

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Table 1: Flow-chart describing the types of calcium incoronary artery

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Table 2: Optical coherence tomography-based choroidal vascularity index score

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Step 2: Assessment of lesion length, choose proper landing zones with minimal plaque burden or plaque-free zone

Selecting the landing zones-visually scan for the largest luminal area, choose landing zones with healthy tissue (i.e., EEL visualization) or minimal plaque burden. In the absence of EEL to represent healthy tissue find the largest lumen to avoid areas of TCFA or lipid pools so as to not land, stent edge in these high risk areas [Figure 6].
Figure 6: Un-healthy landing zones

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Step 3: Assessment of Diameter based upon EEL/luminal

To measure vessel diameter, take EEL measurements at each reference (lumen if EEL not visible) zone, and to decide stent diameter, use the distal reference measurement to select stent diameter [Figure 7].
Figure 7: Choose leading zones without plaque or with minimal plaque burden

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An example of pre stent OCT analysis showed in our case, Lesion Length-29 mm, Proximal Ref Diameter-LD-3.7, Distal REF Diameter-LD-3.2 [Figure 8]. Stent Selected: Length-34 mm, Diameter-3.5, Proximal half of the stent post dilatation balloon with 4 mm NC.
Figure 8: Pre stent optical coherence tomography analysis of a patient to select appropriate stent length and diameter

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To decide stent diameter and post dilation balloon diameter, for distal balloon and stent, use distal reference measurement and for selecting proximal balloon size for expansion of proximal half of stent use proximal reference measurement.


  EEL Measurements Top


  1. Average two perpendicular EEL measurements
  2. Round down to the next quarter size, unless already at a stent size.



  Lumen Measurements Top


  1. Use automatic measurements at distal reference
  2. Round up to the next quarter size, even if already at a stent size.


Postpercutaneous coronary intervention Optical coherence tomography run to optimize (medial edge dissection-apposition-expansion)

Step 4: Assessment of medial dissection

If significant medial dissection present, cover with additional stent particularly if dissection penetrates medial layer, and is >1 quadrant arc (particularly in LM or ostial LAD/LCX or distal dissections) [Figures 9] and [Figure 10].
Figure 9: Post-percutaneous coronary intervention optical coherence tomography run to optimize

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Figure 10: OCT showing large proximal edge dissection of LMCA despite normal looking LM on angio

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Step 5: Assessment of apposition

If malapposition present, use upsized balloon to correct mal apposition specially, If the gross mal apposition is ≥0.3 mm from wall and longer than 3 mm [Figure 11].
Figure 11: Malapposition of a sent near proximal edge which was corrected with an upsized balloon

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Step 6: Assessment of expansion

≥80% expansion of the stent is acceptable and ≥90% expansion is optimal with reference to proximal and distal diameters. If not achieved, post dilate with non-complaint balloon.

Assessment of the ostium and lesion length of side branch

Properly assess plaque burden of SB ostium and lesion length by pull back study of OCT of SB and Main Branch (MB) to Main Vessel (MV). This will be useful in selecting proper landing zones, stent length, and diameter if two-stent technique required. If SB is not significantly diseased avoid SB stenting.


  Predictors of SB Closure Top


OCT is very useful in assessing carina tip (CT) angle, bifurcation point (BP) angle, BP-CT length to predict SB closure before provisional stenting. SB closure is more likely if CT angle <51°, BP-CT length <1.75 mm, and if more plaque burden of MV/SB at the bifurcation site particularly if large calcific plaque opposite to flow divider at carina.[12] The parallel type carina of SB in which proximal course of SB is concealed behind the carina in the 3 Dimensional (3D) perpendicular image of SB more likely to be associated with carina shift perpendicular type in which proximal SB visualized over the carina.


  The Assessment of stent configuration over SB Orifice Top


The assessment of stent configuration over SB orifice and guidewire re-crossing portion with 3D OCT imaging before Kissing Balloon Inflation (KBI) provides important information to achieve an optimal bifurcation strategy.[13],[14] Proper proximal optimization technique (POT) enlarges the distal site of jailed struts, which increase the likelihood of optimal distal wiring. Stent configuration is classified into two types-(a) Link free carina type, (no link connection on the carina)-Distal guide wire re-crossing is required to provide better stent apposition to the lateral wall after KBI. (b) Link connecting carina type (link connection is location between the carina and proximal stent strut) no difference in stent apposition regardless of guide wire re-crossing position, and KBI with distal guide wire re-crossing in the link connecting type has potential risk of stent deformation [Figure 12].
Figure 12: Assessment of stent configuration over SB orifice

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  Crush Evaluation Top


In crush, techniques post crushing OCT run shows very clearly the length of crushed segment in the MV and adequacy of crushed segment of SB stent proximal portion in MV. If crush is inadequate due to under-sized balloon, helps in choosing the appropriate balloon size, and upsizing of balloon required to do repeat crushing to ensure crushing is adequate prior to implanting MB-MV stent. Length of adequately crushed Diagonal 1 (D1) stent-3 mm in proximal LAD extending up to LAD ostium [Figure 13].
Figure 13: Crush evaluation including length

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  Stent Deformation Top


OCT runs after stent implantation can show stent deformation either shortening or longitudinal by showing multiple layers of overlapped stent struts at the site of deformation. Most often observed at the proximal edge of the stent due to guide catheter, old NC balloon, bigger balloons hitting the stent edge while pulling and pushing manipulations particularly when there is no proper alignment and with jailed wire in situ.[14] Multiple strut layers of stent in Proximal LAD-after correction with 4.5 mm × 10 mm NC balloon [Figure 14].
Figure 14: Longitudinal stent dislodgement

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Case I: Assessment of left main coronary artery thrombus with anterior STEMI

Forty-nine-year-old female, known diabetic came with complaints of chest pain, CAD-ACS-evolved AWMI with window period of more than 24 h, 2D Echo– RWMA in LAD territory, mild LV dysfunction with EF– 48%. O/I: Hb-11.5 g/dl, WBC-10700 cells/cmm, Trop-I: 10.08 ng/ml, NT-pro BNP-1553 pg/ml, S. Cr-0.64 mg/dl, RBS-382 mg/dl, Hb1Ac– 11%.

On 2nd day, angio revealed 70%–80% thrombotic lesion of Ostium of LMCA, mid LAD 50% lesion, D1-95% lesion with faint flow [Figure 15]. In view of large thrombus burden with post infarct angina immediate stenting was differed, and treated with IC Tenectaplase (TNK) 10 mg and Abciximab 10 ml. Next day check angio revealed totally re canalized thrombus of LMCA with mild narrowing of ostium of LM [Figure 15], OCT showed lipid rich plaque of Ostio-proximal LMCA with a totally re canalized LMCA thrombus, and partially re canalized thrombus in D1 ostia at LAD-D1 bifurcation with markedly improved diagonal flow and radiolucency at the ostium of D1. OCT showed MLA of ostium of LMCA was about 9 mm2, thrombus in D1 ostium could be due to embolized thrombus from LMCA [Figure 16] site which was treated with additional dose of IC abciximab 10 ml and patient was discharged on 6th day in a stable status without any cardio-vascular symptoms.
Figure 15: Coronary angiogram pre and post thrombolysis

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Figure 16: Post thrombolysis OCT analysis of LM and LAD-D1 bifurcation

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In view of the absence of significant narrowing of ostio-proximal LMCA with MLA more than6 mm2 revascularization of LM was differed. OCT image did not reveal any plaque rupture; STEMI might be due to plaque erosion with thrombus formation which was totally recanalized at LMCA site with partial recanalization of thrombus at D1 site. OCT guided us to manage this case with thrombolytic therapy and avoided interventional/surgical option. OCT insights the cause of LMCA thrombus by revealing underlying plaque morphology. The majority of STEMI cases are due to lipid-rich plaque with TCFA leading to plaque rupture (40%–45%), plaque erosion (15%–20%), and eruptive CN (7%–10%) with thrombus formation. In minority of cases, STEMI may be due to other causes such as SCAD, coronary spasm, and coronary emboli.

EROSION trial showed that the majority of patients (92.5%) with ACS caused by plaque erosion managed with aspirin and Ticagrelor without stenting remained free of major adverse cardiac events for <1 year and suggests medical management without invasive approach may be an alternative option in these patients.

CLIMA study involving more than 1000 patients identified certain OCT high-risk features– Intimal cap thickness of <75 μm, stenosis severity, long lipid rich plaque, and OCT define macrophages as predictors of the future adverse hard clinical events, death, and target lesion-related myocardial infections.

Case II: Assessment of in-stent restenosis of ostium of left main coronary artery

Seventy-two-year-old male, hypertensive presented with acute chest pain and shortness of breath. ECG-ST-T depression in anterior leads, 2D Echo was normal, EF-58%. TMT was positive for inducible ischemia. Investigations-RBS-168 mg/dl, B. Urea-62 mg/dl, S. Cr-1.31 mg/dl, eGFR-54. CAG-90% ISR of o LMCA, LAD-Proximal total occlusion with retrograde filling from RCA, LCX-well patent stent without any significant disease, and 70% narrowing of proximal RCA [Figure 17].
Figure 17: Coronary angiogram showing LAD, LCX & RCA

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PCI was performed through RFA-Route, 7Fr JL 3.5 guiding catheter, LCX was wired with 0.014” Sion Blue, pre dilated with 2.5 mm × 10 mm Tazuna balloon. Pre OCT showed that ostium of LM was not covered with earlier LM DES which resulted in severe edge restenosis of LMCA, and three layers of stents were visible, innermost one is covered stent which was used to seal coronary perforation during the previous PCI [Figure 18]. Further dilatations of LAD were done with 2.5 and 3.5 mm balloons, LMCA dilated with 3.5 mm × 10 mm Cutting balloon and 3.5 mm × 30 mm DEB (Magic Touch). LMCA stenting was done with 4.0 mm × 15 mm Orsiro Stent, post dilated with 4.5 mm × 12 mm NC Trek Balloon. Post-OCT showed well expanded Ostium and distal LMCA with under-expanded shaft of LM stent, which was further expanded with high-pressure balloon inflation using 4.5 mm × 12 mm NC Trek. Post procedure angio views showed well-implanted stents with TIMI-III flow without any dissection.
Figure 18: Pre OCT showed that ostium of LM was not covered with earlier LM DES which resulted in severe edge restenosis of LMCA and three layers of stents were visible, inner most one is covered stent which was used to seal coronary perforation during previous PCI

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Many times it would be difficult to obtain optimal images of LM ostium due to guide position, inadequate clearance of contrast particularly in patients with short LMCA. Good LMCA ostial images can be obtained by high flow contrast injections (i.e., 6 ml/s), keeping proximal one third to half of the OCT catheter inside guiding catheter, and remaining half to two thirds of distal portion extending into proximal LAD with good alignment of guide with LMCA, and in some cases guide extension catheter will be helpful.

Post PCI run of OCT revealed adequate covering of ostium of LMCA with present stent which is well apposed and expanded without any dissection [Figure 19]. The patient is under regular medical management and follow-up without any CV symptoms for 4 years.
Figure 19: Post OCT showed well expanded Ostium and distal LMCA with under-expanded shaft of LM stent, which was further expanded with high pressure balloon inflation using 4.5X12mm NC Trek

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Patients with LM lesions who are undergoing provisional stenting of distal LM without extending stent to ostium of LM may present with proximal edge restenosis during follow-up due to not covering underestimated ostio-proximal lesions of LM on angio guidance. IVI helps in such situations in choosing a proper landing zone without significant plaque burden thereby reduces future restenosis. Takagietal showed the efficiency of the combination of POT and full coverage of ostium of LM on the reduction of ISR in ostium of LM group compared to propensity score-adjusted group that was not treated with this strategy

Case III: Assessment of percutaneous coronary intervention of in-stent restenosis of ostium of left circumflex following left main coronary artery bifurcation stenting

Sixty-four-year-old, female, known hypertensive, and diabetic presented with recent onset of effort chest pain associated with shortness of breath, past history of LM bifurcation PCI with 2 DES 2 years earlier with T-stenting. ECG-NSTEMI. 2D Echo-Normal LV Function, EF-60%. CAG-LMCA and LAD-well patent stent with no significant disease, LCX-ISR with total occlusion at ostium with retrograde filling of distal vessel, RCA– Normal [Figure 20].
Figure 20: Coronary angiogram followed by coronary angioplasty with DEB and DES

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  Procedure Top


RFA-Route, 7Fr EBU 3.5, Initially, attempted to cross CTO of LCX with Sion and Fielder XT wire, finally crossed with Gaia I using microcatheter support and it was exchanged with Sion blue, Fielder FC wire placed in LAD. Pre dilatation of LCX with 1.25 mm × 10 mm and 2.25 mm × 10 mm Tazuna Balloons. The distal stent of LCX was dilated with 2.5 × 15 mm DEB magic touch, uncovered portion of mid-LCX segment between proximal and distal stents of LCX stented with 2.75 mm × 18 mm Yukon Choice Elite. DEB kissing balloon dilatation carried out with 3.0 mm × 20 mm Magic Touch placed in LAD and 2.5 mm × 15 mm Magic touch placed in LCX [Figure 20]. OCT study following DEB kissing showed under-expanded LCX ostium with an MLA of 2.49 mm2 [Figure 21] which was expanded further with 2.5 mm × 12 mm score flex cutting balloon which resulted in well expanded ostium of LCX with an MLA of 5.6 mm2. Final kissing balloon dilatation done with 3.5 mm × 10 mm NC Trek Balloon in LAD and 3.0 mm × 10 mm NC Trek balloon in LCX [Figure 20]. OCT showed well apposed and expanded stent without edge dissection [Figure 22]. Final FKB was done with two DEBs, post angio showed well-implanted stents with TIMI-III flow without any dissection. The patient was discharged on 3rd day post procedure in a stable status and has been under follow-up for the past 4 years without any CV symptoms.
Figure 21: OCT study following DEB kissing showed under-expanded LCX ostium with an MLA of 2.49 mm2

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Figure 22: OCT showed well apposed and expanded stent without edge dissection

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KBI after cross over stenting

Stent struts at ostium of LCX after LM crossover stenting impacted the narrowing of the ostial area at follow-up OCT study and main pathological predictors for LM stent failure are mal apposition and struts crossing an ostium of LCX. The 3D OCT imaging facilitates the achievement of complete removal of jailed struts and fully apposed struts in the bifurcation segment, compared to 2D imaging or angio guidance.

OCT helped us in achieving an adequate expansion of LCX ostium, under-expansion is the most common cause of ISR and stent thrombosis in complex LM bifurcation lesions, and LCX is the most common site of under expansion which occurs in 33% of patients. It would be preferable to achieve post bifurcation PCI MSA of LM more than 8 mm2, LM confluence more than 7 mm2, LAD ostium more than 6 mm2 and LCX ostium more than 5 mm2 or aim to achieve mean reference diameter of stented area at least more than 80% compared to proximal and distal reference areas. Under expansion in two-stent technique group is associated with increased incidence of ISR which is 46% compared to 6% in single stent technique group [Figure 23].
Figure 23: Criteria for stent under-expansion at the distal LM bifurcation

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IVI is more useful in patient with stent failure in identifying mechanisms of ISR; Neo-intimal growth, neo-atherosclerosis lesions, under-expansion of the stent, and progression of disease at stent edges, and guides in choosing an appropriate treatment plan. ST is most commonly due to under-expansion, mal-apposition, uncovered struts with endothelium, or neo-atherosclerosis with plaque rupture or PR at the SER segment.

Case IV: Assessment of provisional stenting of left main bifurcation

Sixty-five-year-old male presented with CAD-ACS-NSTEMI, recent onset of chest pain associated with shortness of breath. Hb-12.5 g/dl, blood urea-14 mg/dl, S. Cr-0.83 mg/dl, eGFR-92 ml/min, RBS-86 mg/dl, 2D Echo-No RWMA, normal, EF-61%. CAG-LMCA-Normal, LAD-Proximal to Mid 80% lesion involving LAD-D1 bifurcation, LCX-Normal, RCA-Normal [Figure 24].
Figure 24: Coronary angiogram showing LAD-D1 bifurcation

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Procedure performed through RFA route, using 7Fr EBU 3.5 guiding catheter, check angiogram revealed LAD-Proximal to Mid 80% lesion which was crossed with 0.014 cm × 190 cm “Turntrac wire, D1 was wired with 0.014” BMW wire. Pre OCT showed long segment fibrotic plaque from proximal to mid LAD [Figure 25].
Figure 25: Pre OCT showed long segment fibrotic plaque from proximal to mid LAD

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In provisional stenting OCT assessment of bifurcation prior to PCI helps in predicting SB closure. Plaque burden of ostio-proximal segment of SB, plaque burden of MV at bifurcation, spiky carina, short BP-CT angle distance <1.75 mm, CT angle <51°, bifurcation angle will guide in choosing PS versus two stent technique. BP-CT Length-3 mm, CT Angle-more than70°, -SB closure unlikely Predilatation done with 2.5 mm × 15 mm Tazuna Balloon, 3.0 mm × 15 mm Angiosculpt Cutting Balloon. Proximal LAD stenting was done with 3.0 mm × 48 mm Xience Xpedition Stent, distal LAD stenting done with 3.0 × 12 mm Xience Xpedition Stent [Figure 26]. Post dilatation was done with 4.0 mm × 08 mm, 3.5 mm × 12 mm NC Trek balloons. Kissing balloon dilatation done with 2.5 mm × 15 mm Tazuna Balloon in D1 and 3.5 mm × 12 mm NC Trek balloon in LAD. Post OCT showed no edge dissection, no residual thrombus [Figure 27] and 73% expansion with mal apposition of 39% which was corrected with postdilatation using 4.5 × 08 mm NC Trek [Figure 11].
Figure 26: OCT assessment of bifurcation prior to PCI helps in predicting SB closure followed by Coronary angioplasty

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Figure 27: Post stenting OCT showed well apposed, under-expanded at proximal edge with no medial edge dissection at both stent edges

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The assessment of guidewire re-crossing point, link connection, and jailing struts on the SB ostium using 3D OCT image is added as a more meticulous step [Figure 28]. Post procedure angio showed well-implanted stents with TIMI-III flow without any dissection. The patient was discharged on 3rd post procedure in a stable status.
Figure 28: Assessment of guide wire re-crossing point, link connection and jailing struts on the SB ostium using 3D OCT image is added as a more meticulous step

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Case V: Assessment of left main proximal stent edge dissection

Fifty-five-year-old female, known case of Stable ischemic heart disease, Diabetes, and Hypertensive with recent onset of unstable angina for 4 days. ECG-normal, 2D Echo–Normal with EF-60%, Trop I-positive, O/I: Hb-9.8 g/dl, RBS-342 mg/dl, S. Cr-1.03 mg/dl, eGFR-61 ml/min, CAG-TVD with diffuse disease of proximal to distal LAD, tight lesion of LCX ostium with distal total occlusion, large OM branch, and mild lesion of mid RCA.

Pre stenting OCT to LAD was done which showed long segment fibro-lipid plaque in Proximal-mid LAD [Figure 29]. OCT assessment of bifurcation prior to PCI helps in predicting SB closure [Figure 30]
Figure 29: Pre stenting OCT to LAD was done which showed long segment fibro-lipid plaque in Proximal - mid LAD

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Figure 30: OCT assessment of bifurcation prior to PCI helps in predicting SB closure

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Distal LMCA bifurcation stenting was done with V stenting using 2.75 mm × 23 mm Xience Xpedition Stent in LAD and 2.0 mm × 30 mm Resolute onyx in LCX, after adequate pre dilatation of LAD and LCX. Post high pressure FKB, angio showed well patent LAD and LCX stents without any dissection of LMCA and distal edge of LAD and LCX stents with good antegrade flow. However, post stenting OCT run showed significant proximal edge medial dissection in distal LMCA with angle more than 60°, more than 5 mm length, and width 0.74 mm [Figure 10] requiring LMCA-LAD additional stenting otherwise it might lead to stent thrombosis and ISR.

Post stenting intravascular imaging (IVUS/OCT) reveals mal apposition, under expansion, edge dissections and rectifying these problems can improve acute and long term outcomes, and many times these are not detected by routine angio. OCT helped us in covering LMCA dissection with additional stenting by crushing ostial portion of LCX stent, after re-crossing LCX ostium through stent struts, followed by FKB and POT of LMCA.

OCT showing clear images of LMCA bifurcation, MLA of distal LM, MLA of LAD ostium 3.8 mm, MLA of ostial LCX– 1.5 mm2 and visible struts slightly abutting onto the LAD ostium [Figure 31].
Figure 31: OCT for assessment of severe ISR of ostium of LCX and LM

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Clearly visible extension of intramural hematoma to distal LM after LAD stenting which is not very clearly seen on angiographic views except for mild narrowing of distal LM [Figure 32].
Figure 32: OCT assessment of Intramural Hematoma in LM

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Assessment of ISR of LCX ostium post-BVS follow-up status– no visible BVS struts with severe ISR of LCX– MLA 1.5 mm2, LD 1.4 mm [Figure 33]. OCT showing fully expanded and apposed stent following LM to LCX provisional stenting for ISR of ostium of LCX (post-BVS follow-up). MSA of LMCA 12 mm2, SD 3.9 mm, MSA of ostium of LCX 9.3 mm2, SD 3.4 mm, proximal LCX MSA 8.3 mm2, SD 3.3 mm [Figure 34].
Figure 33: ISR of LCX ostium by OCT

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Figure 34: Post stenting ISR lesion of ostium of LCX

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Post angio-sculpt plaque modification showed extension of dissection and intramural hematoma to distal LM which required extension of LAD stent to LM to cover distal LM dissection to avoid future recurrence of proximal edge restenosis [Figure 35].
Figure 35: Post angio-sculpt assessment of proximal LAD and distal LM dissection

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OCT showed very tight narrowing after ectatic segment of proximal LAD which was stented, MLA of LMCA is 7.1 mm2 and MLA of ostium of LAD 4.4 mm2. Post stenting FFR assessment showed negative value, hence stenting of LM and ostial LAD was avoided [Figure 36].
Figure 36: OCT assessment of tandem lesions with ectasia of proximal LAD with narrowing of LM to decide LM-LAD provisional stenting vs LAD stenting

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Post stenting angio image showed haziness of proximal LAD stent edge at distal LM bifurcation site which could be due to dissection/thrombus/plaque-prolapse. OCT showed red thrombus at the proximal edge of the stent, managed with extending additional stent overlapping proximal LAD stent to LM [Figure 37].
Figure 37: Post stenting angio image showed haziness of proximal LAD stent edge at distal LM bifurcation site

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Angio showed ambiguous hazy lesion. OCT revealed Recanalized thrombus with an organized thrombus of LM with MLA of mid-LM 3.8 mm2 and MLA of LAD. Managed with provisional stenting of LM to LAD and achieved mid-LM MSA 13 mm2 and proximal LAD MSA 10 mm2 [Figure 38].
Figure 38: Angio showed ambiguous hazy lesion, OCT revealed Recanalized thrombus with organised thrombus of LM

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IVUS-guided PCI, is more often used to guide coronary interventions and has been correlated with improved outcome. The retrospective analysis of MAIN-COMPARE study showed a low death rate in patients who underwent LM PCI with DES in the IVUS group compared to angio guided group.[7] In a patient-level pooled analysis of four registries, IVUS-guided LM PCI has associated with higher freedom from cardiac death, MI and TLR at 3 years, and also showed a significant reduction in stent thrombosis.[15] In recent analysis from the SCAAR study group, IVUS-guided LM PCI was associated with reduction in the composite endpoint of total death rate, need for revascularization and stent thrombosis (HR 0.65, confidence interval 0.50–0.84) and all-cause death.[16]

However, experience and evidence of OCT is limited compared to IVUS which has been widely used for quiet long time in the field of interventional cardiology. CLI-OPCI study of 670 patients showed OCT guided PCI was superior to angio-guided in terms of cardiac death and MI at 1 year (6.6% v/s 13%,).[17] OPINION trial showed non inferiority of OCT guided PCI in terms of TVF 5.2% in the OCT group v/s 4.9% in the IVUS-guided PCI at 12 months' follow up.[18] The ILLUMIEN III study also showed the noninferiority of OCT guided group v/s IVUS group regarding the MSA achieved.[19] The ROCK I study analyzed 267 LM patients, and a total of 112 patients had angiographic follow-up at 6 months. A total of 55 patients had OCT guidance, and the remaining 57 patients had angio-guided procedures. In the control group, 10 patients (17.5%) underwent LM PCI with IVUS guidance. OCT helped in obtaining optimal stent deployment and improved angiographic outcomes in terms of Late Lumen Loss (LLL), binary restenosis, and percent diameter stenosis after 6 months. In particular, the rate of significant restenosis was only 3.5% in the OCT group, compared to 12.9% in standard care, and confirmed the angiographic superiority of OCT guidance during distal LM stenting, when compared to a standard treatment strategy including IVUS in a minority of patients.[20] In Rocket study, the beneficial impact of OCT guidance on LLL was more relevant in the distal segment of the LM. Dato et al. analyzed 122 patients with intermediate LM lesions, showing the feasibility of OCT in this setting, and also showing a good correlation with clinical outcome as regards the initial decision-making process.[21] LEMON Multicenter study of 70 patients showed the efficacy of OCT guided PCI for mid and distal LM showed that OCT guidance for LM PCI was feasible, safe and was successful with primary end point was procedural success defined as residual stenosis <50% plus TIMI grade 3 flow in all branches plus adequate stent expansion on OCT was achieved in 86% patients. Similarly, OCT showed adequate expansion in 86%, mal apposition in 24%, and medial edge dissection in 30%, and it modified operator strategy in 26% of patients with 1-year survival free from major clinical adverse events of 98.6%.[22]

The expert consensus group stated that IVUS and OCT are equivalent and both superior to CAG guidance. OCT guidance is currently proposed by the EBC to support bifurcation lesion PCI and might expand to Distal LMS lesion [Figure 39].
Figure 39: The most relevant targets to be addressed during post DES optimization

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  Conclusions Top


Although the experience of OCT usage for the assessment of LMCA is very limited it is being used by more and more operators throughout the world due to very high-resolution images especially in patients with distal LMCA disease. It is a very valuable imaging technology in assessing LM, MV, and side branch plaque morphology and plaque burden to decide single versus two stent technique, guides plaque modification strategies and in crossing side branch struts (proximal vs. distal), crush evaluation and identifying LSD, edge dissections, malapposition, and expansion of the stent which can influence acute and long-term outcomes of DES implantation. We feel this will play a great role in guiding LMCA interventions.

Acknowledgment

The author would like to thank Mr. Manikandhar Pendyala and Mr. Chandrashekar Challa for their assistant in making this article.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26], [Figure 27], [Figure 28], [Figure 29], [Figure 30], [Figure 31], [Figure 32], [Figure 33], [Figure 34], [Figure 35], [Figure 36], [Figure 37], [Figure 38], [Figure 39]
 
 
    Tables

  [Table 1], [Table 2]



 

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  In this article
Abstract
Introduction
Image Acquisition
Optical Coherenc...
EEL Measurements
Lumen Measurements
Predictors of SB...
The Assessment o...
Crush Evaluation
Stent Deformation
Procedure
Conclusions
References
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