Assessment of coronary arterial plaque by optical coherence tomography

Low molecular weight dextran provides similar optical coherence tomography coronary imaging compared to radiographic contrast media

BACKGROUND

Optical coherence tomography (OCT) coronary imaging requires displacement of red blood cells from the vessel lumen. This is usually accomplished using radiographic contrast. Low molecular weight dextran has low cost and is safe in low volumes. In the present study, we compared dextran with contrast for coronary OCT imaging.

METHODS

Fifty-one vessels in 26 patients were sequentially imaged using manual injection of radiographic contrast (iodixanol) and dextran. OCT images were analyzed at 1 mm intervals to determine the image clarity (defined as a visible lumen border > 270°) and to measure the lumen area and lumen diameter. To correct for the refractive index of dextran, the dextran area measurements were multiplied by 1.117 and the dextran length measurements were multiplied by 1.057.

RESULTS

A total of 3,418 cross-sections (1,709 with contrast and 1,709 with dextran) were analyzed. There were no complications related to OCT imaging or to contrast or dextran administration. Clear image segments were observed in 97.0% vs. 96.7% of the cross-sections obtained with contrast and dextran, respectively (P = 0.45). The mean lumen areas were also similar: 6.69 ± 1.95 mm(2) with iodixanol vs. 7.06 ± 2.06 mm(2) with dextran (correlation coefficient 0.984).

CONCLUSIONS

The image quality and measurements during OCT image acquisition are similar for dextran and contrast. Dextran could be used instead of contrast for OCT imaging, especially in patients in whom contrast load minimization is desired.

Automated tissue characterization of in vivo atherosclerotic plaques by intravascular optical coherence tomography images

Intravascular optical coherence tomography (IVOCT) is rapidly becoming the method of choice for the in vivo investigation of coronary artery disease. While IVOCT visualizes atherosclerotic plaques with a resolution <20µm, image analysis in terms of tissue composition is currently performed by a time-consuming manual procedure based on the qualitative interpretation of image features. We illustrate an algorithm for the automated and systematic characterization of IVOCT atherosclerotic tissue. The proposed method consists in a supervised classification of image pixels according to textural features combined with the estimated value of the optical attenuation coefficient. IVOCT images of 64 plaques, from 49 in vivo IVOCT data sets, constituted the algorithm's training and testing data sets. Validation was obtained by comparing automated analysis results to the manual assessment of atherosclerotic plaques. An overall pixel-wise accuracy of 81.5% with a classification feasibility of 76.5% and per-class accuracy of 89.5%, 72.1% and 79.5% for fibrotic, calcified and lipid-rich tissue respectively, was found. Moreover, measured optical properties were in agreement with previous results reported in literature. As such, an algorithm for automated tissue characterization was developed and validated using in vivo human data, suggesting that it can be applied to clinical IVOCT data. This might be an important step towards the integration of IVOCT in cardiovascular research and routine clinical practice.

Frequency-domain optical coherence tomography assessment of human carotid atherosclerosis using saline flush for blood clearance without balloon occlusion

FD-OCT is a new imaging technique that allows unprecedented in vivo microlevel assessment of human carotid plaque morphologic patterns and stent-vessel interactions. Prior reports describing the use of this technique have used balloon occlusion of the target vessel or iodinated contrast media to facilitate imaging. We report, for the first time, in vivo FD-OCT imaging of human carotid arteries without the use of iodinated contrast material or balloon occlusion techniques.

Coronary superficial and spotty calcium deposits in culprit coronary lesions of acute coronary syndrome as determined by optical coherence tomography

The characteristics of coronary artery calcium responsible for vulnerable plaque remain incompletely elucidated. We used optical coherence tomography to investigate the characteristics of coronary calcium in acute myocardial infarction (AMI), unstable angina pectoris (UAP), and stable angina pectoris (SAP). We evaluated calcium deposits in the culprit lesions (30-mm segment) using optical coherence tomography in 187 patients with AMI (n = 44), UAP (n = 73), or SAP (n = 70). The arc, area, and length of calcium were significantly smaller in those with AMI and UAP than in those with SAP (p <0.001). The number of spotty calcium deposits (with an arc of <90°) per patient was significantly larger in the AMI and UAP groups than in the SAP group (p <0.001). The number of large calcium deposits (with an arc of >90°) per patient was significantly lower in the AMI and UAP groups than in the SAP group (p <0.001). The minimum distance between the inner edge of the calcium and the luminal surface was significantly shorter in the AMI and UAP groups than in the SAP group (p <0.001). Plaque rupture frequency correlated positively with the number of spotty calcium deposits (r = 0.479, p <0.001) and inversely with the number of large calcium deposits (r = -0.219, p = 0.003). In conclusion, calcium was very spotty and more superficial in the culprit lesions of AMI and UAP. These characteristics of calcium might play an important role in the pathogenesis of plaque vulnerability.

[Optical coherence tomography. Bases and applications of a new intravascular imaging technique]

Coronary angiography is the reference technique for the diagnosis of coronary disease. However, the majority of acute coronary syndromes involve angiographically non-significant lesions. It is also the technique of choice for guiding the implantation of endovascular prostheses and their later monitoring. Optical coherence tomography is an interferometric imaging technique that penetrates tissue approximately 2-3mm and provides axial and lateral resolution. It is able to distinguish different tissue types, such as fibrous, lipid-rich, necrotic, or calcified tissue. Optical coherence tomography is able to recognize a variety of features of atherosclerotic plaques that have been associated with rapid lesion progression and clinical events, such as thin cap fibroatheroma, fibrous cap thickness, dense macrophage infiltration, and thrombus formation. Currently, there is growing interest in the value of optical coherence tomography in the area of coronary intervention, where the technique offers significant advantages over more widespread intravascular diagnostic techniques such as intravascular ultrasound. Its higher resolution permits to recognize periprocedural complications, such as microdissection of the coronary artery, stent malapposition, and neointimal hyperplasia, making this tool one of the most promising techniques in the intravascular diagnosis.

Optical coherence tomography for characterization of cardiac allograft vasculopathy after heart transplantation (OCTCAV study)

BACKGROUND

Optical coherence tomography (OCT) is a novel intravascular imaging modality with excellent spatial resolution. This study explored the utility of OCT in cardiac transplantation for the detection and characterization of early changes associated with coronary allograft vasculopathy (CAV).

METHODS

Fifteen consecutive patients, 1 to 4 years after transplant with no angiographic evidence of CAV, underwent successful OCT imaging using the Fourier-domain OCT system (C7-XR, St. Jude Medical, St. Paul, MN) in the left anterior descending artery. Analysis included measurements of the lumen, intima, and media layers, and characterization of atherosclerotic plaques. Patients were stratified by intima-to-media (I/M) ratio and classified as normal (≤1) or abnormal (>1).

RESULTS

Patients were a mean of 2.8 years after transplant, 58 years old, and 92% were men. OCT imaging revealed 8 of 15 patients had intimal hyperplasia with an I/M ratio >1. Comparing those with I/M ratio of ≤1 and >1, the median (interquartile range) intimal thickness was greater (75 [70-101] vs 206 [97-269]μm, p = 0.03), whereas the media thickness was no different (72 [70-103] vs 94 [73-113]μm, p = 0.53). In addition, 7 of 15 patients had lipid-rich or calcified atherosclerotic plaques.

CONCLUSIONS

OCT provides high-resolution quantitative imaging of the coronary arteries and its use allows for detailed assessment of the coronary artery wall and early morphologic changes that occur after cardiac transplantation. The clinical predictive value of these OCT-derived measurements remains to be determined.

Coronary optical coherence tomography: minimally invasive virtual histology as part of targeted post-mortem computed tomography angiography

Social, cultural and practical barriers to conventional invasive autopsy have led to considerable interest in the development of minimally invasive radiological techniques as an alternative to the invasive autopsy for determining the cause of death. Critical to accurate diagnosis in this context is detailed examination of coronary anatomy and pathology. Current computed tomography and magnetic resonance imaging approaches have significantly advanced minimally invasive autopsy practice but have limited spatial resolution. This prohibits assessment at a microscopic level, meaning that histological assessment is still required for detailed analysis of, for example, coronary plaque rupture or dissection. Coronary optical coherence tomography (OCT) is used in the living during percutaneous coronary interventions to provide high-resolution coronary imaging, but this technique for obtaining virtual histology has not, to date, been translated into minimally invasive autopsy practice. We present a first description of minimally invasive post-mortem coronary OCT and discuss the potential for this technique to advance current practice.

Impact of lesion length on functional significance in intermediate coronary lesions

BACKGROUND

Myocardial fractional flow reserve (FFR) is useful in the evaluation of coronary lesion ischemia. However, the impact of lesion length on FFR has not been adequately assessed.

HYPOTHESIS

We hypothesized that lesion length would influence functional significance in intermediate coronary lesions.

METHODS

FFR measurements were assessed in 136 patients (163 lesions) with stable angina who had >40% stenotic coronary lesion by quantitative coronary angiography (QCA). One hundred sixty-three lesions were classified as intermediate (40%-70% stenosis; n=107; group I) or significant (≥70%; n=56; group S) by QCA. We assessed the relationships between lesion length, coronary stenosis, and FFR in these 163 lesions.

RESULTS

Regression analysis revealed an inverse correlation between the percentage of diameter stenosis (%DS) and FFR in group S (r = -0.83, P < 0.0001). In group I, no significant correlation was found between %DS and FFR (r = -0.06, P = 0.55), whereas lesion length was significantly inversely correlated with FFR (r = -0.79, P < 0.0001). Receiver operating characteristic curve analysis demonstrated that the best cutoff value for predicting an FFR value <0.80 was a lesion length >16.1 mm in group I (sensitivity, 86%; specificity, 94%).

CONCLUSIONS

These study findings suggest that lesion length has a physiologically significant impact on intermediate-grade coronary lesions.

Optical coherence tomography imaging in asymptomatic patients with carotid artery stenosis

Assessment and treatment plan for asymptomatic patients with carotid stenosis are based on angiography at the present time. However, angiography or other imaging modalities are limited with their resolution to detect high-risk plaque features. Intravascular optical coherence tomography (IVOCT) recently emerged as a novel imaging modality with a unique resolution to identify vulnerable plaque characteristics. We report use of IVOCT in two separate asymptomatic patients with carotid stenosis with two different plaque types.

Safety and feasibility of a new non-occlusive technique for facilitated intracoronary optical coherence tomography (OCT) acquisition in various clinical and anatomical scenarios

AIMS

To facilitate OCT images acquisition we developed a novel, simplified, non-occlusive technique based on manual infusion of a viscous isosmolar solution. The aims of the present study was to address the safety and efficacy of non-occlusive OCT images acquisition modality in a patient population with complex coronary lesions, and in various clinical scenarios.

METHODS AND RESULTS

OCT assessment was performed with the LightLab OCT Imagewire in 64 patients. The imaging acquisition technique was aimed at target lesion and proximal and distal reference segments. OCT images were deemed of good quality if they allowed both an accurate measurement of luminal area and a qualitative classification of the superficial plaque components.In 60 patients (93.7%), the procedure was successful. The mean images acquisition time was 5.3+/-1.4 minutes. No major complications such as death, myocardial infarction or major arrhythmias were recorded. The average length of imaged segments was 28.6+/-6.1 mm and 95.1% of the imaged segments were deemed of sufficient quality to evaluate luminal area and plaque morphology (intra-observer and inter-observer variability 0.71, p<0.0001 and 0.68, p<0.0001 respectively).Conclusions. The non-occlusive modality of OCT image acquisition is safe and effective, and promises to simplify the complex current occlusive technique, leading to a marked reduction of procedural time.

Intravascular frequency-domain optical coherence tomography assessment of atherosclerosis and stent-vessel interactions in human carotid arteries

BACKGROUND AND PURPOSE

Carotid artery-related stroke is largely an embolic disease that has been correlated with inflammation, plaque rupture, and thrombus formation in "vulnerable" atherosclerotic plaque. Nevertheless, current guidelines for carotid revascularization in asymptomatic patients rely on the calculation of stenosis for risk assessment, a parameter that has been viewed with increasing skepticism. Intravascular OCT is an imaging technique that offers high axial resolution (10 μm), allowing an unprecedented micron-level assessment of human carotid plaque morphology. This observational article reports the first successful use of the newest iteration of this technology, FDOCT without balloon occlusion to assess human carotid artery disease and carotid stent-vessel interaction in vivo.

MATERIALS AND METHODS

Four patients with asymptomatic carotid artery disease and ambiguous noninvasive and/or angiographic data underwent carotid FDOCT to assess risk and to formulate a treatment strategy.

RESULTS

Findings include the unexpected demonstration of TCFAs, plaque rupture, thrombus, inflammation, and marked tissue prolapse through stent struts in patients without high-risk factors by conventional criteria, as well as low-risk features in a patient with a high-risk noninvasive study. The procedures were performed without safety issues or special accommodations for vessel occlusion.

CONCLUSIONS

The present study demonstrates the technical feasibility of FDOCT in cervical carotid arteries. As such, this technology holds the promise of not only clarifying ambiguous data in individual patients but of providing data that might call for a future paradigm shift in the assessment of asymptomatic carotid artery disease.

Intracoronary optical diagnostics current status, limitations, and potential

Optical coherence tomography (OCT), is a novel intravascular imaging modality analogous to intravascular ultrasound but uses light instead of sound. This review details the background, development, and status of current investigation using OCT, and discusses advantages, limitations, and likely future developments. It provides indications for possible future clinical use, and places OCT in the context of current intravascular imaging in what is a rapidly changing field of investigation.

Effect of strut thickness on neointimal atherosclerotic change over an extended follow-up period (≥ 4 years) after bare-metal stent implantation: intracoronary optical coherence tomography examination

BACKGROUND

Neointima inside the bare-metal stents (BMSs) can transform into atherosclerotic tissue during an extended follow-up because of a persistent inflammatory reaction to the metal. We sought to investigate whether strut thickness may impact on the atherosclerotic change in neointima 4 years or more after BMS implantation using optical coherence tomography.

METHODS

Forty-six stented lesions of 41 patients with BMS ≥ 4 years after implantation who underwent optical coherence tomography were enrolled in the study. The strut was defined as thin when less than 100 μm and thick when ≥ 100 μm. According to these criteria, stents were divided into 2 groups (thin strut n = 19, thick strut n = 27). Neointimal tissue was categorized into normal neointima, characterized by a signal-rich band without signal attenuation, or lipid-laden intima, with marked signal attenuation and a diffuse border. Intimal disruption, thrombus, and neovascularization were also evaluated.

RESULTS

The mean period after implantation was 98.2 ± 25.8 months in the thin-strut group and 91.1 ± 22.8 months in the thick-strut group (P = .330). Lipid-laden intima (70% vs 32%, P = .016), thin-cap fibroatheroma-like intima (59% vs 16%, P = .0056), and intimal disruption (48% vs 16%, P = .031) were observed more frequently in the thick-strut group than in the thin-strut group, but no significant difference was observed in the frequency of thrombus. Although peristrut neovascularization was a common finding in both groups (thick vs thin 81% vs 79%, P = 1.000), the frequency of intraintima neovascularization tended to be higher in the thick-strut group (67% vs 42%, P = .135).

CONCLUSIONS

A thinner strut thickness may have favorable effects on neointimal atherosclerotic changes after BMS implantation.

The role of optical coherence tomography in coronary intervention

Optical coherence tomography (OCT) is an optical analog of intravascular ultrasound (IVUS) that can be used to examine the coronary arteries and has 10-fold higher resolution than IVUS. Based on polarization properties, OCT can differentiate tissue characteristics (fibrous, calcified, or lipid-rich plaque) and identify thin-cap fibroatheroma. Because of the strong attenuation of light by blood, OCT systems required the removal of blood during OCT examinations. A recently developed frequency-domain OCT system has a faster frame rate and pullback speed, making the OCT procedure more user-friendly and not requiring proximal balloon occlusion. During percutaneous coronary intervention (PCI), OCT can provide detailed information (dissection, tissue prolapse, thrombi, and incomplete stent apposition [ISA]). At follow-up examinations after stent implantation, stent strut coverage and ISA can be assessed. Several OCT studies have demonstrated delayed neointimal coverage following drug-eluting stent (DES) implantation vs. bare metal stent (BMS) placement. While newer DESs promote more favorable vascular healing, the clinical implications remain unknown. Recent OCT studies have provided insights into restenotic tissue characteristics; DES restenotic morphologies differ from those with BMSs. OCT is a novel, promising imaging modality; with more in-depth assessments of its use, it may impact clinical outcomes in patients with symptomatic coronary artery disease.

Optical coherence tomography: from research to practice

Optical coherence tomography (OCT) is a high-resolution imaging technique with great versatility of applications. In cardiology, OCT has remained hitherto as a research tool for characterization of vulnerable plaques and evaluation of neointimal healing after stenting. However, OCT is now successfully applied in different clinical scenarios, and the introduction of frequency domain analysis simplified its application to the point it can be considered a potential alternative to intravascular ultrasound for clinical decision-making in some cases. This article reviews the use of OCT for assessment of lesion severity, characterization of acute coronary syndromes, guidance of intracoronary stenting, and evaluation of long-term results.

Intravascular optical coherence tomography detection of atherosclerosis and inflammation in murine aorta

OBJECTIVE

The goal of this study was to evaluate the feasibility of imaging the aorta of apolipoprotein E-deficient (ApoE(-/-)) mice for the detection of atherosclerosis and macrophages using optical coherence tomography (OCT) compared with histology.

METHODS AND RESULTS

Atherosclerosis was induced by high-fat diet in 7-week-old ApoE(-/-) mice for 10 (n=7) and 22 (n=7) weeks. Nine-week-old ApoE(-/-) mice (n=7) fed a standard chow diet were used as controls. OCT images of a 10-mm descending aorta in situ were performed in 4 mice for each, and plaque and macrophages were determined at 0.5-mm intervals. Automated detection and quantification of macrophages were performed independently using a customized algorithm. Coregistered histological cross-sections were stained with hematoxylin-eosin, Mac-3, and von Kossa. Three mice in each group had en face OCT imaging to detect macrophages, which were compared with lipid-positive area with Sudan IV. OCT images were successfully acquired in all mice. OCT and histology were able to discriminate macrophages and plaque among the 3 groups and showed excellent correlation for (1) visual detection of plaque (r=0.98) and macrophages (r=0.93), (2) automated detection and quantification of macrophages by OCT versus Mac-3-positive area (r=0.92), and (3) en face OCT detection of macrophages versus Sudan IV-positive area (r=0.92).

CONCLUSIONS

Murine intra-aortic OCT is feasible and shows excellent correlation with histology for detection of atherosclerotic plaque and macrophages.

The diagnostic value of intracoronary optical coherence tomography

Optical coherence tomography (OCT) is a novel light-based imaging modality for application in the coronary circulation. Compared to conventional intravascular ultrasound, OCT has a ten-fold higher image resolution. This advantage has seen OCT successfully applied in the assessment of atherosclerotic plaque, stent apposition, and tissue coverage, heralding a new era in intravascular coronary imaging. The present article discusses the diagnostic value of OCT, both in cardiovascular research as well as in potential clinical application.The unparalleled high image resolution and strong contrast between the coronary lumen and the vessel wall structure enable fast and reliable image interpretation. OCT makes it possible to visualize the presence of atherosclerotic plaque in order to characterize the structure and extent of coronary plaque and to quantify lumen dimensions, as well as the extent of lumen narrowing, in unprecedented detail. Based on optical properties, OCT is able to distinguish different tissue types, such as fibrous, lipid-rich, necrotic, or calcified tissue. Furthermore, OCT is able to cover the visualization of a variety of features of atherosclerotic plaques that have been associated with rapid lesion progression and clinical events, such as thin cap fibroatheroma, fibrous cap thickness, dense macrophage infiltration, and thrombus formation. These unique features allow the use of OCT to assess patients with acute coronary syndrome and to study the dynamic nature of coronary atherosclerosis in vivo and over time. This permits new insights into plaque progression, regression, and rupture, as well as the study of effects of therapies aimed at modulating these developments.Today's OCT technology allows high detail resolution as well as fast and safe clinical image acquisition. These unique features have established OCT as the gold standard for the assessment of coronary stents. This technique makes it possible to study stent expansion, peri-procedural vessel trauma, and the interaction of the stent with the vessel wall down to the level of individual stent struts, both acutely as well as in the long term, where it is has proven extremely sensitive to the detection of even minor amounts of tissue coverage. These qualities render OCT indispensable to addressing vexing clinical questions such as the relationship of drug-eluting stent deployment, vascular healing, the true time course of endothelial stent coverage, and late stent thrombosis. This may also better guide the optimal duration of dual anti-platelet therapy that currently remains unclear and relatively empirical.In the future, OCT might emerge, parallel to its undisputed position in research, as the tool of choice in all clinical scenarios where angiography is limited by its nature as a two-dimensional luminogram.

A case of in-stent neointimal plaque rupture 10 years after bare metal stent implantation: intravascular ultrasound and optical coherence tomographic findings

Neointimal hyperplasia mainly develops within several months of coronary stent deployment, after which it stabilizes. Although it was widely accepted, particularly during the bare-metal stent (BMS) era, that in-stent restenosis (ISR) generally does not present as an acute coronary syndrome (ACS), but rather as a gradual recurrence of angina symptoms, recent data have shown that a substantial number of patients with ISR present as ACS. There has also been consistent postmortem evidence of plaque rupture secondary to atherosclerotic change within the neointima of a BMS. We report here a case of ACS in which intravascular ultrasound and optical coherent tomographic assessments revealed neointimal atherosclerotic change and ruptured plaque 10 years after BMS deployment.

Thin-cap fibroatheroma as high-risk plaque for microvascular obstruction in patients with acute coronary syndrome

BACKGROUND

Plaque contents can cause microvascular impairment, which is an important determinant of clinical outcomes in patients with acute coronary syndrome (ACS). We hypothesized that percutaneous coronary intervention (PCI) for thin-cap fibroatheroma (TCFA) could easily disrupt the fibrous cap and expose the contents of plaque to coronary flow, possibly resulting in microvascular obstruction (MVO). The purpose of this study was to investigate whether TCFA was associated with MVO after PCI in patients with ACS.

METHODS AND RESULTS

We enrolled 115 patients with ACS who were successfully recanalized with PCI. The patients were divided into a ruptured plaque group (n=59), a nonrupture with TCFA group (n=21), and a nonrupture and non-TCFA group (n=35), according to optical coherence tomography findings of the culprit lesion. Using contrast-enhanced MRI, we assessed MVO. There were no statistically significant differences in patient characteristics. The nonrupture with TCFA group more frequently presented MVO (ruptured plaque, 27%; versus nonrupture with TCFA, 43%; versus non-TCFA and nonrupture, 9%; P=0.012). The prevalence of MVO increases as cap thickness decreases.

CONCLUSIONS

TCFA is more frequently associated with MVO after PCI. TCFA is a high-risk plaque for MVO after PCI in patients with ACS.

Optical coherence tomography imaging in acute coronary syndromes

Optical coherence tomography (OCT) is a high-resolution imaging technique that offers microscopic visualization of coronary plaques. The clear and detailed images of OCT generate an intense interest in adopting this technique for both clinical and research purposes. Recent studies have shown that OCT is useful for the assessment of coronary atherosclerotic plaques, in particular the assessment of plaque rupture, erosion, and intracoronary thrombus in patients with acute coronary syndrome. In addition, OCT may enable identifying thin-cap fibroatheroma, the proliferation of vasa vasorum, and the distribution of macrophages surrounding vulnerable plaques. With its ability to view atherosclerotic lesions in vivo with such high resolution, OCT provides cardiologists with the tool they need to better understand the thrombosis-prone vulnerable plaques and acute coronary syndromes. This paper reviews the possibility of OCT for identification of vulnerable plaques in vivo.

Optical coherence tomography analysis of attenuated plaques detected by intravascular ultrasound in patients with acute coronary syndromes

Background. Recent intravascular ultrasound (IVUS) studies have demonstrated that hypoechoic plaque with deep ultrasound attenuation despite absence of bright calcium is common in acute coronary syndrome. Such “attenuated plaque” may be an IVUS characteristic of unstable lesion. Methods. We used optical coherence tomography (OCT) in 104 patients with unstable angina to compare lesion characteristics between IVUS-detected attenuated plaque and nonattenuated plaque. Results. IVUS-detected attenuated plaque was observed in 41 (39%) patients. OCT-detected lipidic plaque (88% versus 49%, P < 0.001), thin-cap fibroatheroma (48% versus 16%, P < 0.001), plaque rupture (44% versus 11%, P < 0.001), and intracoronary thrombus (54% versus 17%, P < 0.001) were more often seen in IVUS-detected attenuated plaques compared with nonattenuated plaques. Conclusions. IVUS-detected attenuated plaque has many characteristics of unstable coronary lesion. The presence of attended plaque might be an important marker of lesion instability.

Current status of optical coherence tomography

Optical coherence tomography (OCT) is a novel imaging technology based on low-coherence interferometry that use near-infrared light in real-time, and allows cross-sectional in-situ visualization of the vessel wall at the microscopic level. OCT provides 10-fold higher resolution than intravascular ultrasound which is currently the most used modality for intra-coronary imaging. OCT offers the obvious advantages when characterizing precise plaque microstructure and distinguishing various type of plaques. OCT is also being assessed for its potential role in the understanding of neointimal coverage, vascular healing and the progression of atherosclerosis in coronary vasculature after stenting on the micron scale. These unique capabilities could be helpful in guiding coronary management and interventions. Recent improvement in next generation OCT technology, such as frequency-domain OCT, will allow for a simple imaging procedure, providing more useful information and complementing other modalities on both clinical and research applications for the cardiologists.

Intravascular optical imaging technology for investigating the coronary artery

There is an ever-increasing demand for new imaging methods that can provide additional information about the coronary wall to better characterize and stratify high-risk plaques, and to guide interventional and pharmacologic management of patients with coronary artery disease. While there are a number of imaging modalities that facilitate the assessment of coronary artery pathology, this review paper focuses on intravascular optical imaging modalities that provide information on the microstructural, compositional, biochemical, biomechanical, and molecular features of coronary lesions and stents. The optical imaging modalities discussed include angioscopy, optical coherence tomography, polarization sensitive-optical coherence tomography, laser speckle imaging, near-infrared spectroscopy, time-resolved laser induced fluorescence spectroscopy, Raman spectroscopy, and near-infrared fluorescence molecular imaging. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in the evaluation of the coronary artery in the future.

First-in-man evaluation of intravascular optical frequency domain imaging (OFDI) of Terumo: a comparison with intravascular ultrasound and quantitative coronary angiography

AIMS

The objective of this study is to evaluate the feasibility and safety of imaging human coronary arteries in vivo by optical frequency domain imaging (OFDI) in comparison to intravascular ultrasound (IVUS). OFDI has been recently developed to overcome the limitations of conventional time-domain optical coherence tomography (OCT), namely the need for proximal balloon occlusion. The Terumo-OFDI system is capable of acquiring images with high-speed automated pullback (up to 40 mm/sec) and requires only a short injection (3-4 sec) of small amount of x-ray contrast (9-16 ml).

METHODS AND RESULTS

Nineteen patients who underwent stent implantation were enrolled. IVUS/OFDI were performed before and after stenting. The incidences of any adverse event and angiographic adverse findings were recorded. Lumen area (LA) was measured by IVUS and OFDI at 1 mm intervals in the stented segments (n=19) as well as in the proximal, distal, and to-be-stented segments (n=40). In addition, lumen area in the stented segment was also measured by edge (E-) and video-densitometric (VD-) quantitative coronary angiography (QCA). The OFDI images were obtained without any adverse event related to imaging procedures. Post stenting (n=19), minimal LA (MLA) measured by OFDI (5.84 ± 1.89 mm2) was larger than that of E-QCA (4.16 ± 1.46 mm2, p<0.001) and VD-QCA (4.92 ± 1.55 mm2, p<0.05). It was smaller than IVUS-MLA (6.26 ± 2.01 mm2, N.S.) but the correlation between the two measurements was highly significant (R2=0.82, p<0.001).

CONCLUSIONS

The OFDI imaging is feasible both before and after stenting and has a promising safety profile. The OFDI provided clear high resolution images and robust lumen measurements.

Impact of coronary plaque morphology assessed by optical coherence tomography on cardiac troponin elevation in patients with elective stent implantation

BACKGROUND

Mild elevations of cardiac troponin frequently occur after percutaneous coronary intervention (PCI), and patients with elevated post-PCI biomarkers have a worse prognosis. We used optical coherence tomography (OCT) to study the relationship between pre-PCI plaque morphology and post-PCI cardiac troponin I elevations.

METHODS AND RESULTS

One hundred thirty-one patients with normal pre-PCI cardiac troponin I levels underwent OCT before nonemergency stent implantation. Clinical and OCT findings were compared between patients with (n=31, 23.7%) and without (n=100, 76.3%) post-PCI cardiac troponin I of >3 × upper reference limit (post-PCI myocardial infarction [MI]). After PCI, long-term follow-up data were collected. Post-PCI MI was associated with angiographic lesion length, type B2/C lesions, presence of thin-cap fibroatheroma, and fibrous cap thickness. In multivariable analysis, presence of thin-cap fibroatheroma (odds ratio, 10.47; 95% confidence interval, 3.74 to 29.28; P<0.001) and type B2/C lesions (odds ratio, 3.74; 95% confidence interval, 1.41 to 9.92; P=0.008) were predictors of post-PCI MI. At a median follow-up of 12 months, cardiac event-free survival was significantly worse in patients with post-PCI MI (log-rank test χ(2)=8.9; P=0.003). Cox proportional hazards analysis showed that post-PCI MI (hazard ratio, 3.67; 95% confidence interval, 1.39 to 9.65; P=0.009) and ejection fraction (hazard ratio, 0.96; 95% confidence interval, 0.92 to 0.99; P=0.029) were independent predictors of adverse cardiovascular events during follow-up.

CONCLUSIONS

Type B2/C lesions and the presence of OCT-defined thin-cap fibroatheroma can predict post-PCI MI in patients treated with elective stent implantation, who may require adjunctive therapy after otherwise successful PCI.

Thrombus Aspiration during Percutaneous coronary intervention in Acute non-ST-elevation myocardial infarction Study (TAPAS II)-Study design

Background and Objective. The Thrombus Aspiration during Percutaneous coronary intervention in Acute myocardial infarction Study (TAPAS) has shown that thrombus aspiration improves myocardial perfusion and clinical outcome compared with conventional primary percutaneous coronary intervention (PCI) in patients with ST-segment-elevation myocardial infarction. Impaired myocardial perfusion due to spontaneous or angioplasty-induced embolisation of atherothrombotic material also occurs in patients with non-ST-elevation myocardial infarction (NSTEMI). The aim of this study is to determine whether thrombus aspiration before stent implantation will result in improved myocardial perfusion in patients with NSTEMI compared with conventional PCI.Study design. The study is a single-centre, prospective, randomised trial with blinded evaluation of endpoints. The planned inclusion is 540 patients with acute NSTEMI who are candidates for urgent PCI. Patients are randomised to treatment with manual thrombus aspiration or to conventional PCI. The primary endpoint is the incidence of myocardial blush grade 3 after PCI. Secondary endpoints are coronary angiographic, histopathological, enzymatic, electrocardiographic and clinical outcomes including major adverse events at 30 days and one year.Implications. If thrombus aspiration leads to significant improvement of myocardial perfusion in patients with acute NSTEMI it may become part of the standard interventional approach. (Neth Heart J 2009;17:409-13.).

Optical coherence elastography: current status and future applications

Optical coherence tomography (OCT) has several advantages over other imaging modalities, such as angiography and ultrasound, due to its inherently high in vivo resolution, which allows for the identification of morphological tissue structures. Optical coherence elastography (OCE) benefits from the superior spatial resolution of OCT and has promising applications, including cancer diagnosis and the detailed characterization of arterial wall biomechanics, both of which are based on the elastic properties of the tissue under investigation. We present OCE principles based on techniques associated with static and dynamic tissue excitation, and their corresponding elastogram image-reconstruction algorithms are reviewed. OCE techniques, including the development of intravascular- or catheter-based OCE, are in their early stages of development but show great promise for surgical oncology or intravascular cardiology applications.

Plaque and thrombus evaluation by optical coherence tomography

Intravascular Optical Coherence Tomography has been explored as an imaging tool for vessel wall and thrombus characterization. OCT enables a high resolution arterial wall imaging, and light properties allow tissue characterization. It has been proved one of the most valuable imaging modalities for the evaluation of vulnerable plaque and thrombus. OCT has a unique capacity in volumetric quantification of calcium, and unlike ultrasound, light can easily penetrate calcified plaques. Finally, this review paper will address aspects of the validation method of plaque characterization and potential pitfalls and put in perspective new approaches that may help the evolution of the field.

Intracoronary optical coherence tomography, basic theory and image acquisition techniques

Optical coherence tomography (OCT) imaging is showing great potential as an alternative or complementary tool to intravascular ultrasound (IVUS) for aiding in stent procedures and future diagnosis/treatment of atherosclerosis. Here, we describe the basic theory behind OCT imaging and explain important parameters such as axial resolution, lateral resolution and sensitivity. Also, we describe several image acquisition techniques that have been adopted for OCT imaging.

Optical coherence tomography: its value in intravascular diagnosis today

Optical coherence tomography is a recently developed high-resolution intravascular diagnostic technique. Initially, it was mainly used for characterizing atherosclerotic plaque because it served a number of functions, from identifying plaque with high lipid content to detecting macrophage accumulation, both of which are associated with plaque instability. Currently, there is growing interest in the value of optical coherence tomography in the area of coronary intervention, where the technique offers significant advantages over more widespread intravascular diagnostic techniques such as intravascular ultrasound: its higher resolution means that the vessel lumen diameter can be measured more precisely, periprocedural complications such microdissection of the coronary artery can be detected, stent apposition relative to the vessel wall can be optimized, neointimal hyperplasia can be detected after stent implantation, and neointimal thickness can be measured. It would therefore appear to be a very useful technique for interventional cardiologists. This review article considers the technical details of the technique and its applications, and compares it with other intravascular diagnostic techniques.

Relationship Between Arterial and Fibrous Cap Remodeling

Background—

Positive arterial remodeling and thin fibrous cap are characteristics of rupture-prone or vulnerable plaque. The natural course of the fibrous cap thickness and the relationship between serial arterial remodeling and changes in fibrous cap thickness are unknown. Therefore, the purpose of this study was to evaluate the relationship between changes in fibrous cap thickness and arterial remodeling by using optical coherence tomography (OCT) and intravascular ultrasound (IVUS) during 6-month follow-up.

Methods and Results—

Both IVUS and OCT examinations were performed on 108 vessels from 36 patients with ischemic heart disease who underwent percutaneous coronary intervention. Fifty-eight fibroatheromas were selected from 82 nonsignificant, nonculprit lesions (angiographic diameter stenosis, 25% to 75%; plaque burden, >40% by IVUS). Fibroatheroma was defined by OCT as lipid-rich plaque in >1 quadrant that has lipid. Thickness of the fibrous cap was measured by OCT. IVUS and OCT examinations were repeated at 6-month follow-up. Serial changes and relationships between IVUS indices and fibrous cap thickness were investigated. Overall, fibrous cap thickness (98.1±38.9 to 96.9±44.5 μm) as well as IVUS indices did not change significantly within 6 months. The percent changes in fibrous cap thickness correlated negatively and significantly ( r =−0.54; P <0.0001; generalized estimating equation adjusted, r =−0.42; P =0.001) with the percent changes in external elastic membrane cross-sectional area.

Conclusions—

Arterial remodeling is related to changes in fibrous cap thickness. Positive arterial remodeling is not only an adaptive process, but also related to thinning of the fibrous cap.

Clinical classification and plaque morphology determined by optical coherence tomography in unstable angina pectoris

Unstable angina pectoris (UAP) is categorized with the Braunwald classification. However, the association of clinical presentation and plaque structure/function has not yet been elucidated in relation to cause. We used optical coherence tomography to investigate this relation. One hundred fifteen patients with primary UAP were categorized according to the Braunwald classification. Patients with class I UAP had the highest frequency of ulcers without fibrous cap disruption (p = 0.003) and the smallest minimum lumen area (class I, median 0.70 mm(2), quartiles 1 to 3 0.42 to 1.00; class II, 1.80 mm(2), 1.50 to 2.50; class III, 2.31 mm(2), 1.21 to 3.00; p <0.001). Patients with class II UAP had the highest frequency of coronary spasm (p <0.001) and the lowest frequency of thrombi (p <0.001). Patients with class III UAP had the highest frequency of plaque ruptures (p <0.001), the thinnest fibrous cap (class I, median 140 microm, quartile 1 to 3 90 to 160; class II, 150 microm, 120 to 160; class III, 60 microm, 40 to 105; p <0.001), and the highest frequency of thin cap fibroatheromas (p <0.001) and spotty calcifications (p <0.001). In conclusion, the structures/functions of culprit lesions on optical coherence tomograms differ in the Braunwald classes of UAP. Plaque vulnerability, progressive stenosis, and vasoconstriction may be related to the cause of the distinct presentations.