Cardiac Optical Coherence Tomography (OCT): Difference between revisions
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OCT offers the highest resolution among intravascular imaging modalities, providing excellent detection of fibrous cap and lipid core features, with good utility for identifying calcium and thrombus, making it uniquely suited for detailed plaque characterization. [59] | OCT offers the highest resolution among intravascular imaging modalities, providing excellent detection of fibrous cap and lipid core features, with good utility for identifying calcium and thrombus, making it uniquely suited for detailed plaque characterization. [59] | ||
{| class="wikitable" | {| class="wikitable" | ||
! colspan="5" | | |||
! colspan="5" |'''Clinical utility in detection of vulnerable plaque feature''' | |||
|- | |- | ||
!'''Imaging Technique''' | |||
!'''Technology''' | |||
!'''Wavelength (µm)''' | |||
!'''Penetration (mm)''' | |||
!'''Resolution (µm)''' | |||
!'''Fibrous Cap''' | |||
!'''Lipid Core''' | |||
!'''Inflammation''' | |||
!'''Calcium''' | |||
!'''Thrombus''' | |||
|- | |- | ||
!'''Coronary Angiography''' | |||
| | |X-ray | ||
| | |0.00001–0.01 | ||
| | |0.0 | ||
| | |>500 | ||
| | |– | ||
| | |– | ||
| | |– | ||
| | | + | ||
| | | +++ | ||
|- | |- | ||
!'''IVUS''' | |||
| | |Ultrasound | ||
| | |35–80 | ||
| | |10.0 | ||
| | |100–200 | ||
| | | + | ||
| | | ++ | ||
| | |– | ||
| | | +++ | ||
| | |– | ||
|- | |- | ||
!'''OCT''' | |||
|'''Infrared''' | |'''Infrared''' | ||
|'''1.3''' | |'''1.3''' | ||
| Line 219: | Line 219: | ||
|'''++''' | |'''++''' | ||
|- | |- | ||
!'''NIRS''' | |||
| | |Near-infrared | ||
| | |0.8–2.5 | ||
| | |1.0–2.0 | ||
| | |N/A | ||
| | |– | ||
| | | +++ | ||
| | |– | ||
| | |– | ||
| | |– | ||
|- | |- | ||
!'''Raman Spectroscopy''' | |||
| | |Near-infrared | ||
| | |0.75–1.0 | ||
| | |1.0–2.0 | ||
| | |N/A | ||
| | |– | ||
| | | +++ | ||
| | | - | ||
| | |– | ||
| | |– | ||
|- | |- | ||
!'''IV-MRI''' | |||
| | |MRI | ||
| | |N/A | ||
| | |0.25 | ||
| | |100 | ||
| | | + | ||
| | | ++ | ||
| | | ++ | ||
| | | ++ | ||
| | | + | ||
|- | |- | ||
!'''Angioscopy''' | |||
| | |Optical | ||
| | |0.4–0.7 | ||
| | |0.0 | ||
| | |10–50 | ||
| | | + | ||
| | | + | ||
| | | - | ||
| | |– | ||
| | | +++ | ||
|- | |- | ||
!'''Thermography''' | |||
| | |Infrared | ||
| | |0.8–2.5 | ||
| | |1.0 | ||
| | |500 | ||
| | |– | ||
| | |– | ||
| | | +++ | ||
| | |– | ||
| | |– | ||
|} | |} | ||
Legend: | Legend: | ||
Revision as of 01:27, 29 April 2025
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor-In-Chief: Parth Vikram Singh, MBBS[2]
Overview
Optical Coherence Tomography (OCT) is a medical imaging methodology that uses a specially designed catheter with an optical fiber at its distal end to emit near-infrared light. The proximal end of the catheter is connected to a computerized imaging console that detects the light backscattered from within the vessel wall. OCT allows high-resolution visualization of the coronary artery structure by generating cross-sectional images from inside the blood vessels. This technology enables highly detailed, real-time visualization of coronary morphology by capturing optical reflections of tissue microstructures, allowing precise assessment of the endothelium, plaque burden, thin-cap fibroatheromas (TCFA), thrombus, calcium, and stent positioning.[17-23] Compared to intravascular ultrasound (IVUS), OCT offers superior axial resolution (~10-20 µm vs. 100-150 µm for IVUS), though with shallower penetration depth (1-2 mm vs. 4-8 mm for IVUS).
Available Platforms
OCT imaging utilizes near-infrared light (typically ~1,300 nm) to detect backscattered signals from tissue, offering unmatched spatial resolution. OCT imaging quality can be compromised by structures that absorb infrared light, such as thrombus, lipid-rich necrotic core, or calcified plaques.[1] Additionally, because blood scatters infrared light and interferes with image clarity, it must be cleared from the vessel using radiocontrast or, in some cases, saline before acquiring OCT images.
Two main systems dominate the OCT market:
- Frequency-domain OCT (FD-OCT): Most commonly used, faster, and allows real-time imaging.
- Time-domain OCT (TD-OCT): Obsolete in clinical settings.
Major commercial platforms include Abbott's Dragonfly catheter (used with the ILUMIEN system) and Terumo's LUNAWAVE system. Recent advancements in OCT technology have led to hybrid systems that integrate additional imaging modalities such as IVUS (e.g., Novasight Hybrid by Conavi Medical and Dual Sensor by Terumo), near-infrared spectroscopy (HyperVue by SpectraWave), and near-infrared fluorescence (Canon Medical). These combinations allow clinicians to harness the complementary strengths of each modality simultaneously. Furthermore, OCT-based vessel reconstructions are now being utilized to compute virtual fractional flow reserve (vFFR) through computational fluid dynamics, offering the potential to assess both the anatomical features and physiological significance of coronary lesions in a single imaging session.
Assessment of Atherosclerosis
The arteries of the heart (the coronary arteries) are the most frequent imaging target for OCT. OCT is used in the coronary arteries to determine the amount of atheromatous plaque built up at any particular point in the epicardial coronary artery. The progressive accumulation of plaque within the artery wall over decades is the setup for vulnerable plaque which, in turn, leads to myocardial infarction and stenosis (narrowing) of the artery (known as coronary artery lesions). OCT is of use to determine both plaque volume within the wall of the artery and/or the degree of stenosis of the artery lumen. It can be especially useful in situations in which angiographic imaging is considered unreliable; such as for the lumen of ostial lesions or where angiographic images do not visualize lumen segments adequately, such as regions with multiple overlapping arterial segments. It is also used to assess the effects of treatments of stenosis such as with hydraulic angioplasty expansion of the artery, with or without stents, and the results of medical therapy over time.
Arteries can either "positively remodel" or "negatively remodel". If there is an outward expansion of the artery to accommodate the plaque, this is referred to as positive or outward, or expansive modeling. Until the plaque occupies 40 to 50% of the volume of the artery there is no luminal encroachment.in contrast, if the lumen is encroached upon this is called negative, and word or constrictive remodeling.
The characteristic bright-dark-bright trilaminar pattern seen in a normal coronary artery corresponds to light reflections from its three distinct layers: the intima, media, and adventitia.
In atherosclerotic vessels, the normal arterial architecture becomes disrupted, and OCT reveals distinct morphological patterns that correspond to various types of plaque. These vessel wall morphologies include signal-rich (bright) low-attenuating areas characteristic of fibrous plaques (figure 2A), signal-poor (dark), high-attenuation regions with an overlying fibrous cap indicative of lipid-rich plaques (figure 2B), and well-defined, signal-poor low-attenuation zones representing calcific plaques (figure 2C).[3] Within the lumen, the most frequently observed pathologies include high-attenuation red thrombus, which produces shadowing on the vessel wall, and low-attenuation white thrombus.
Furthermore, OCT’s superior resolution allows precise identification of culprit lesions in acute coronary syndrome (ACS), like plaque rupture, plaque erosion, and eruptive calcified nodules. (figure 4) [5] Recognizing the underlying causes of acute coronary syndrome (ACS) can contribute to more personalized and targeted treatment strategies. OCT is also valuable in assessing patients with spontaneous coronary artery dissection (SCAD) or myocardial infarction with non-obstructive coronary arteries (MINOCA), as it helps clarify the presence and nature of the culprit lesions in cases of non–ST-segment elevation MI (NSTEMI).[1] Finally, OCT is valuable in detecting high-risk vulnerable plaques, such as thin-cap fibroatheromas (TCFAs), that have a propensity to rupture and trigger acute coronary syndromes (ACS).
In the interpretation of coronary Optical Coherence Tomography (OCT), the first step is to determine whether all three layers of the arterial wall—the intima, media, and adventitia—are clearly visualized. If all three layers are visible, the vessel is likely either a normal artery or one containing a fibrous plaque, both of which maintain relatively preserved architecture. However, if the layers cannot be fully visualized, the next step is to identify where the signal loss or attenuation is occurring.
If the signal change is located within the lumen, its characteristics help differentiate thrombus types. High attenuation in the lumen suggests the presence of red thrombus, which typically absorbs more light. Conversely, low attenuation in the lumen is indicative of a white thrombus, which is less optically dense.
If the signal change occurs within the vessel wall, the pattern again provides diagnostic clues. High attenuation within the wall points toward a lipid-rich plaque, which scatters light significantly. On the other hand, low attenuation in the wall is characteristic of calcified plaque, which appears as a sharply delineated low-signal region with minimal backscatter.
This stepwise assessment enables clinicians to classify plaques and thrombi with precision and guide decision-making during percutaneous coronary interventions.
Indications
Intravascular OCT is used to guide PCI in a standardized approach. This standardized method is often summarized using the mnemonic MLD-MAX, where the pre-PCI focus is on MLD: Morphology, Length, and Diameter, and the post-PCI evaluation centers on MAX: Medial dissection, Apposition, and eXpansion. Pre-procedural OCT imaging plays a key role in planning PCI by:
(1) evaluating lesion morphology to guide optimal lesion preparation,
(2) identifying suitable proximal and distal landing zones with minimal disease for stent placement,
(3) accurately measuring vessel diameter to select appropriate balloon and stent sizes.
Following PCI, OCT imaging is instrumental in optimizing stent outcomes by detecting
(1) edge dissections at the stent margins that may necessitate additional stenting,
(2) areas of stent malapposition, and
(3) stent underexpansion that may require further post-dilation.
Pre-PCI lesion assessment:
To Assess the Severity of Lesions
Angiography often underestimates the severity of lesions. The angiogram only evaluates the lumen and does not evaluate the plaque burden in an artery. If a lesion is present OCT will generally demonstrate that 50 to 60% of the volume of the artery is made up of plaque both proximal and distal to the lesion.
OCT has been related to defects on nuclear imaging and Doppler flow wire measurements of coronary flow reserve (CFR) and fractional flow reserve (FFR) to validate its accuracy.
The consensus view is that any minimum lumen area (MLA) < 4 mm² in an artery that is > 3 mm on angiography (excluding the left main) is a significant stenosis.
To Assess the Underlying Morphology of Lesions
OCT is more sensitive than angiography in the assessment of calcium, particularly the presence of calcium deep in the wall of the artery. The sensitivity of angiography is approximately 25% if there is one quadrant of calcium present, the sensitivity is 50% if there are two quadrants of calcium, the sensitivity is 60% if there are three quadrants of calcium and finally the sensitivity is 85% if there are for quadrants calcium. In lesions with predominantly fibrous or lipid-rich plaque, direct stenting or predilatation with an undersized balloon may be sufficient. However, for moderate to severe calcification, specialized plaque modification techniques, such as noncompliant, cutting, or scoring balloons, atherectomy, or intravascular lithotripsy (IVL), are often required. OCT is particularly valuable in these cases, as it provides a more precise evaluation of calcium burden compared to IVUS. An OCT-based calcium scoring system can help guide the need for advanced plaque modification.[15,16] (figure 10) Specifically, lesions with calcium arc >180° (i.e. 50% of circumference), thickness >0.5 mm, and length >5 mm (commonly referred to as the "rule of 5") are more likely to require atherectomy or IVL due to their association with suboptimal stent expansion.To Assess The Length Of Lesions
To accurately measure lesion length, it is essential to select proximal and distal reference segments that have minimal plaque burden and provide clear visualization of the vessel wall. The imaging software typically calculates the distance between these segments automatically, and the operator can adjust them to align with the length of an available drug-eluting stent. This approach helps reduce the risk of stent edge-related complications, such as inflow or outflow disease and the presence of TCFA at the stent margins, which are associated with poorer clinical outcomes. [28-33]
To Assess the Diameter Of Lesions
Device sizing during PCI can be guided using either the external elastic lamina (EEL) or lumen-based measurements. An external elastic lamina (EEL)-guided strategy is preferred over a lumen-guided approach when 2 measurements can be obtained at least one quadrant apart. This approach generally allows for the selection of a balloon or stent approximately 0.5 mm larger, resulting in a larger final lumen area without increasing the risk of complications.[24-26] To select the stent size, the mean EEL diameter of the distal reference segment is measured and then rounded down to the nearest available stent size.[27] If the EEL is not well visualized, often due to plaque-induced signal attenuation, the mean lumen diameter is used instead and rounded up to the next available stent size.[27] The same principles, based on the respective reference diameter measurements, apply when selecting the size of the post-dilation balloon.
Assessment of the left main is associated with the greatest amount of inter and intraobserver variability in angiography. The left main is short, and is often diseased with asymmetric lesions making its assessment on angiography difficult. There may be diffuse disease which may cause an underestimation of the extent of involvement on angiography. While luminal encroachment is defined as a minimum lumen area less than 4 mm² in the epicardial arteries, a minimum lumen area less than 6 mm² in the left main is considered to be significant. A minimum lumen area less than 6 mm² in the left main corresponds with a fractional flow reserve less than 0.75. A minimum lumen area less than 6 mm² also corresponds to a minimum lumen area less than 4 mm² in either the LAD or the circumflex arteries.
Assessment of the diameter of the vessel is particularly useful in research studies such as those evaluating lipid lowering agents. Care must be taken to identify reproducible start and end points for the mechanical pullback to ensure that the same area of the segment is being interrogated.
Post-PCI lesion optimization
To Identify Complications Such as Dissection
Following PCI, the proximal and distal reference segments should be evaluated for signs of medial dissection or intramural hematoma (Fig. 15).[35] Due to its high resolution, OCT can detect post-PCI edge dissections in up to 40% of cases.[36] However, most of these dissections are minor and tend to heal without causing significant clinical consequences.[37,38] That said, major edge dissections observed on OCT are associated with worse clinical outcomes.[39-42] It is generally advised to deploy an additional stent if a large dissection involves more than 60° of the vessel circumference and extends over 3 mm into the medial layer, provided that stenting is not limited by anatomical constraints.[43]
To Guide Adequate Stent Apposition:
Stent malapposition refers to the separation between the stent struts and the vessel wall. [1,44] Although malapposition is frequently observed on OCT following stent implantation (upto 50%),[45] it generally does not increase the risk of stent failure or thrombosis.[46-49] However, certain scenarios, such as proximal malapposition that may hinder future rewiring, extensive malapposition extending more than 3mm in length, or malapposition associated with stent underexpansion, warrants further optimization (Fig. 16). Stent apposition refers to the stent touching the vessel wall while stent expansion refers to the size of the stent. Poor stent apposition is of a greater concern in an artery with a small minimum stent area than in a larger artery. Complete and position obviously may not be possible in aneurysmal segments or ectatic segments.
To Guide Adequate Stent Expansion:
Stent expansion is a key determinant of long-term stent success and can be evaluated using absolute measurements, such as minimum stent area (MSA), or relative metrics like the ratio of MSA to the reference lumen area.[44] According to current European guidelines, optimal stent deployment is defined by either: (1) an MSA > 4.5 mm² on OCT for non–left main lesions (absolute expansion), or (2) an MSA exceeding 80% of the average of the proximal and distal reference lumen areas (relative expansion).[50,60] While absolute MSA is generally a stronger predictor of adverse outcomes, achieving this threshold in smaller vessels may not be feasible, which highlights the clinical relevance of relative stent expansion.[44] Despite multiple criteria for defining adequate relative expansion, success is typically achieved in approximately 50% of cases.[51] (figure 17) An inadequate minimum stent area is associated with a higher risk of stent thrombosis. Insofar as OCT optimizes the minimum stented area, the use of OCT reduces the risk of stent restenosis.
Advantages over Angiography
Arguably the most valuable use of OCT is to visualize plaque, which cannot be seen by angiography. It has been increasingly used in research to better understand the behavior of the atherosclerosis process in living people. OCT enables accurately visualizing not only the lumen of the coronary arteries but also the atheroma (membrane/cholesterol loaded white blood cells) "hidden" within the wall. OCT has thus enabled advances in clinical research providing a more thorough perspective and better understanding.
Unlike angiography, which functions as a luminogram by displaying only the contrast-filled lumen, optical coherence tomography (OCT) offers a much more detailed assessment of the vessel wall and plaque characteristics. OCT can accurately differentiate between various types of plaque, including fibrous, lipid-rich, and calcific components. It is also highly sensitive in detecting thrombi, allowing identification of both red and white thrombus formations. In the context of stent deployment, OCT plays a crucial role by evaluating stent apposition, expansion, and detecting complications such as edge dissections or tissue prolapse. Importantly, OCT enables visualization of vulnerable plaques—particularly thin-cap fibroatheromas (TCFA)—which are defined by a fibrous cap measuring less than 65 µm and are often associated with acute coronary syndromes.
OCT also plays a significant role in evaluating restenosis and stent failure. In the past, angiographic appearances of “restenosis” after angioplasty often reflected not true luminal collapse, but rather the inadequate apposition or incomplete expansion of a stent. OCT enables precise assessment of stent geometry, measuring minimum stent area, identifying tissue prolapse, edge dissections, and malapposition, which angiography frequently misses. These details are pivotal in preventing stent thrombosis and ensuring long-term patency. [7,8]
Furthermore, OCT imaging has advanced our understanding of coronary healing. For example, serial OCT studies have shown how neointimal coverage evolves over time after drug-eluting stent (DES) implantation, helping clinicians evaluate reendothelialization. [9]
OCT's real-time, catheter-based imaging—paired with automated pullback and rapid acquisition—has enabled its integration into routine percutaneous coronary intervention (PCI), where it aids not only in lesion assessment but also in fine-tuning procedural outcomes. Most commercial OCT systems are now equipped with built-in tools for automated detection of stents and contouring of the lumen or external elastic membrane (EEM). Additionally, the use of deep learning algorithms for automated plaque and lesion characterization is an emerging area of ongoing research and development. (Figure 6) [10,13,14]
Disadvantages of OCT
Adoption Barriers Among Clinicians:
A large survey [12] of interventional cardiologists cited the following as key barriers to routine OCT use:
- Higher procedural costs
- Increased procedure time (~15 minutes longer)
- Lack of formal training
- Absence of standardized interpretation guidelines
Cost Considerations:
The FORZA trial reported that OCT-guided PCI incurs higher costs compared to FFR-guided PCI.[11] However, a head-to-head cost-effectiveness analysis between OCT, IVUS, and angiography has not yet been conducted.
Limited Penetration Depth:
Despite its superior resolution, OCT has shallower tissue penetration than IVUS, which can restrict its ability to assess deeper structures.
Need for Blood Clearance:
OCT requires temporary displacement of blood from the imaging field, usually through contrast injection. This makes imaging difficult in:
- Ostial coronary segments since it is difficult to clear the blood from the coronary ostia.
- Caliber of the left main coronary artery may prohibit it from adequate flush clearance.
- Hemodynamically unstable patients where high contrast load may be undesirable.
- Individuals with advanced chronic kidney disease, where contrast use is contraindicated
Challenges in Certain Anatomies:
- Difficulty imaging the aorto-ostial regions due to poor clearance
- Suboptimal results in large-caliber vessels (e.g., left main)
- Limitations in tortuous or ectatic coronary arteries
- Not validated for chronic total occlusion (CTO) revascularization guidance
Flushing Agent Issues:
While alternative agents like normal saline have been explored, they may still result in blood mixing and carry a risk of arrhythmia.
Imaging Artifacts
- OCT artifacts can be broadly classified into two categories: those arising from the interaction of light with the catheter, lumen, or vessel wall, and those resulting from the catheter’s position and movement within the vessel (Figure 11). Certain lumen contents or vessel components can significantly attenuate the OCT signal, creating shadowing effects that obscure the visualization of deeper arterial wall layers.
- Inadequate clearance of blood from the imaging field can lead to signal-rich areas within the lumen, causing interference that reduces image clarity and diminishes the intensity of the OCT signal reaching the vessel wall (Figure 11A, 11B). Additionally, swirling blood, especially during the initiation or completion of the pullback, may mimic the appearance of thrombus or plaque erosion (Figure 11C, 11D). Red thrombus strongly attenuates OCT light, while metallic elements like stent struts and guidewires obstruct light propagation, casting shadows on the underlying tissue.
- The catheter’s position within the vessel and the vessel’s diameter also influences image quality. Excessive force during insertion can lead to catheter prolapse, where the catheter bends or folds within the lumen (Figure 11E). Moreover, irregular catheter movement, whether due to inconsistent rotation or variable pullback speed, can distort images. One specific artifact, known as non-uniform rotational distortion (NURD), manifests as lateral blurring or smearing and is caused by variations in angular velocity of the rotating optical fiber. NURD commonly arises in tortuous or narrow vessels, or when there is resistance from tight hemostatic valves or crimped catheter sheaths (Figure 11F, 11G).
- Another artifact may occur when the OCT catheter is too close to the vessel wall. In such cases, the emitted light may travel nearly parallel to the tissue surface, reducing beam penetration. This can falsely appear as signal attenuation and may be misinterpreted as thin-cap fibroatheroma (TCFA) (Figure 4H). [34]
Method
An OCT system is composed of three main components: the imaging catheter, a motorized drive unit, and dedicated imaging software. Before the procedure, the catheter must be flushed with the same fluid intended for coronary artery flushing—typically radiographic contrast, though saline is occasionally used. Proper engagement of the guide catheter is essential to ensure effective flushing and to prevent catheter disengagement during image acquisition. To enhance image quality and reduce the risk of catheter-induced vasospasm, intracoronary nitroglycerin is typically administered before imaging.
The OCT acquisition process follows a structured sequence: position, purge, puff, and pullback.
1. Position: The OCT catheter is advanced approximately 10 mm distal to the lesion over a coronary guidewire.
2. Purge: The catheter is purged again to eliminate residual air or bubbles.
3. Puff: A small puff of contrast is injected through the guide catheter to verify proper engagement and ensure adequate blood clearance. Occasionally, a guide catheter extension may be necessary to prevent backflow of the flushing agent into the aorta.
4. Pullback: The automated pullback mechanism is then activated. During this phase, contrast or saline is delivered either manually or via an automated injector.
Clinical Evidence
Early studies demonstrated that OCT imaging had a significant impact on procedural decision-making. In the CLI-OPCI study, for instance, post-PCI OCT identified suboptimal features requiring additional intervention in 35% of cases.[52] Moreover, OCT-guided PCI was associated with a lower incidence of myocardial infarction (MI) or cardiac death at one year after adjustment for confounding variables.
The OPINION trial [53] was the first to directly compare outcomes between OCT- and IVUS-guided PCI. It found no significant difference in the primary endpoint of target vessel failure at one year, establishing the noninferiority of OCT guidance relative to IVUS. Similarly, the ILUMIEN III trial [54] demonstrated that OCT-guided PCI was noninferior to IVUS-guided PCI in terms of final minimum stent area (MSA), reinforcing OCT’s role as a viable alternative for intravascular imaging guidance. In the large-scale OCTIVUS trial (n = 1005 for OCT vs. 1003 for IVUS),[55] OCT-guided PCI was again shown to be noninferior to IVUS-guided PCI for the composite primary endpoint of cardiac death, target-vessel MI, or ischemia-driven target-vessel revascularization at one year.
The ILUMIEN IV trial [56], a global, multicenter randomized controlled study, compared OCT-guided versus angiography-guided PCI in high-risk patients or those with complex lesions (n = 1233 vs. 1254). OCT guidance resulted in significantly larger final MSA (5.72 ± 2.04 mm² vs. 5.36 ± 1.87 mm²; P < .001) and greater stent expansion, attributed to the selection of larger stents and more frequent high-pressure postdilation. While the trial showed no significant difference in the primary clinical endpoint of a composite of cardiac death, target-vessel MI, or ischemia-driven target-vessel revascularization at 2 years, it did report a notable reduction in stent thrombosis with OCT guidance. The OCTOBER trial,[57] which enrolled patients with complex bifurcation lesions (n = 600 for OCT, 601 for angiography), found that OCT-guided PCI significantly reduced the composite outcome of cardiac death, target-lesion MI, or ischemia-driven target-vessel revascularization at two years compared to angiography guidance. In the RENOVATE-COMPLEX PCI trial,[58] intravascular imaging guidance (both IVUS [74.5%] and OCT [25.5%]) led to a lower risk of the composite endpoint of cardiac death, target vessel-related MI, or clinically driven target vessel revascularization compared with angiography-guided PCI. Subgroup analysis confirmed consistent benefits across both IVUS and OCT modalities.
Multiple high-quality randomized trials support the use of OCT-guided PCI over angiography-guided strategies, particularly in high-risk patients or those with complex coronary lesions. Additionally, OCT has shown clinical equivalence to IVUS, making it a reliable alternative for intravascular imaging–guided intervention.
Comparison with other imaging modalities
OCT offers the highest resolution among intravascular imaging modalities, providing excellent detection of fibrous cap and lipid core features, with good utility for identifying calcium and thrombus, making it uniquely suited for detailed plaque characterization. [59]
| Clinical utility in detection of vulnerable plaque feature | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Imaging Technique | Technology | Wavelength (µm) | Penetration (mm) | Resolution (µm) | Fibrous Cap | Lipid Core | Inflammation | Calcium | Thrombus |
| Coronary Angiography | X-ray | 0.00001–0.01 | 0.0 | >500 | – | – | – | + | +++ |
| IVUS | Ultrasound | 35–80 | 10.0 | 100–200 | + | ++ | – | +++ | – |
| OCT | Infrared | 1.3 | 1.0–2.5 | <10 | +++ | +++ | + | ++ | ++ |
| NIRS | Near-infrared | 0.8–2.5 | 1.0–2.0 | N/A | – | +++ | – | – | – |
| Raman Spectroscopy | Near-infrared | 0.75–1.0 | 1.0–2.0 | N/A | – | +++ | - | – | – |
| IV-MRI | MRI | N/A | 0.25 | 100 | + | ++ | ++ | ++ | + |
| Angioscopy | Optical | 0.4–0.7 | 0.0 | 10–50 | + | + | - | – | +++ |
| Thermography | Infrared | 0.8–2.5 | 1.0 | 500 | – | – | +++ | – | – |
Legend:
– = Not possible + = Adequate ++ = Good +++ = Excellent
Guidelines and Recommendations
The ACC/AHA 2022 and ESC 2024 guidelines both support the use of intravascular imaging for procedural guidance during PCI, particularly in complex lesions. While the U.S. gives a Class IIa recommendation for both IVUS and OCT, the European guidelines provide a stronger Class I recommendation with Level A evidence for using IVUS or OCT in left main, bifurcation, and long lesions.
Conclusion
OCT is an advanced imaging modality offering unparalleled resolution for intracoronary imaging. It complements angiography and IVUS in guiding PCI, particularly in stent optimization and high-risk plaque detection. Its limitations are offset by its precision and evolving evidence base.
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