Barlis, P.

Multi-modality intra-coronary plaque characterization: A pilot study (Article)

2010-01-07T00:00:00Z

Background: The risk of rupture and subsequent thrombosis of the atherosclerotic coronary plaques is related to the presence of necrotic core with high lipid content. We conducted an exploratory pilot trial to compare the capability for lipid tissue detection using four intra-coronary diagnostic techniques: greyscale intravascular ultrasound (GS IVUS), IVUS radiofrequency data (IVUS RFD) analysis, optical coherence tomography (OCT) and intravascular magnetic resonance spectroscopy (IVMR). Methods: Twenty-four matched target plaques were analyzed with the 4 techniques in non-culprit lesions in five patients with stable angina. Following IVUS pullback, OCT and IVMR was performed. Plaque composition was assessed using established criteria of each technology. Results: Atherosclerotic plaques classified as soft by GS IVUS were mainly composed by fibro-fatty (80%) or necrotic core (20%) by IVUS RFD. These soft plaques were classified as "lipid-rich" by OCT in the majority of cases (80%). IVMR confirmed the presence of lipid with a lipid fraction index ranging between 36 and 79 in these soft plaques. Besides this good agreement for soft plaques, GS IVUS, IVUS RFD and OCT had 100% agreement in the identification of calcified plaques. Conclusion: The present study explored multi-modality imaging of atherosclerotic plaque in-vivo. Assessing specifically lipid-rich plaques, there was generally good agreement for plaque components identified as soft by traditional GS IVUS with RFD and OCT whereas IVMR showed a varying amount of lipid in these regions. Nevertheless there continues to remain inherent variation, namely as a result of the different imaging resolutions and the lack of common nomenclature and classification.

An optical coherence tomography study of a biodegradable vs. durable polymer-coated limus-eluting stent: A LEADERS trial sub-study (Article)

2010-01-01T00:00:00Z

AimsIncomplete endothelialization has been found to be associated with late stent thrombosis, a rare but devastating phenomenon, more frequent after drug-eluting stent implantation. Optical coherence tomography (OCT) has 10 times greater resolution than intravascular ultrasound and thus appears to be a valuable modality for the assessment of stent strut coverage. The LEADERS trial was a multi-centre, randomized comparison of a biolimus-eluting stent (BES) with biodegradable polymer with a sirolimus-eluting stent (SES) using a durable polymer. This study sought to evaluate tissue coverage and apposition of stents using OCT in a group of patients from the randomized LEADERS trial.Methods and resultsFifty-six consecutive patients underwent OCT during angiographic follow-up at 9 months. OCT images were acquired using a non-occlusive technique at a pullback speed of 3 mm/s. Data were analysed using a Bayesian hierarchical random-effects model, which accounted for the correlation of lesion characteristics within patients and implicitly assigned analytical weights to each lesion depending on the number of struts observed per lesion. Primary outcome was the difference in percentage of uncovered struts between BESs and SESs. Twenty patients were included in the analysis in the BES group (29 lesions with 4592 struts) and 26 patients in the SES group (35 lesions with 6476 struts). A total of 83 struts were uncovered in the BES group and 407 out of 6476 struts were uncovered in the SES group [weighted difference-1.4, 95 confidence interval (CI)-3.7 to 0.0, P = 0.04]. Results were similar after adjustment for pre-procedure lesion length, reference vessel diameter, number of implanted study stents, and presence of stent overlap. There were three lesions in the BES group and 15 lesions in the SES group that had ≥5 of all struts uncovered (difference-33.1, 95 CI-61.7 to-10.3, P < 0.01).ConclusionStrut coverage at an average follow-up of 9 months appears to be more complete in patients allocated to BESs when compared with SESs. The impact of this difference on clinical outcome and, in particular, on the risk of late stent thrombosis is yet to be determined. © Published on behalf of the European Society of Cardiology. All rights reserved.

The use of intra-coronary optical coherence tomography for the assessment of sirolimus-eluting stent fracture (Article)

2009-07-24T00:00:00Z

Drug-eluting stents (DES) have made a tremendous impact on the practice of percutaneous coronary intervention. Recently however, long-term DES failures have become a focal point, particularly with restenosis and thrombosis. An uncommon, yet important cause of DES failure is stent fracture. Of the two established first generation DES, the sirolimus-eluting stent (SES) has been particularly linked to cases of stent fracture, likely as a result of its closed cell design compared with other DES employing an open cell system. We present 2 cases of SES fracture confirmed using high-resolution intravascular optical coherence tomography giving unique insights into the in-vivo appearance of this complication.

The Use of Intracoronary Optical Coherence Tomography in Interventional Cardiology: Safety, Feasibility and Clinical Applications (Doctoral Thesis)

2009-05-27T00:00:00Z

Interventional cardiology has witnessed tremendous change since 1977 when Andreas Gruentzig successfully performed the first balloon angioplasty. Whereas initial concerns revolved around maintaining vessel patency with issues of recoil and restenosis, the introduction of stents changed the landscape forever. Inherent with their use, stents, and, more specifically, drugeluting stents (DES), have become central to improved patient outcomes but, at some cost. Catastrophic, yet fortunately still rare complications such as stent thrombosis have re-ignited an intense need for greater scrutiny when developing and, subsequently implanting DES into our patients. The demand for detailed information regarding coronary artery disease has seen intravascular imaging become pivotal at delineating atherosclerosis and tissue responses following stent implantation. In fact, the strategy that relied on angiography alone is evolving to include better confirmation of disease severity and stenting technique. With this, optical coherence tomography (OCT) has grown exponentially with a broad diffusion amongst catheterisation laboratories worldwide. Optical coherence tomography is a procedurally demanding technique. Individual experience is often frustrated initially with disappointing images as a result of inadequate blood clearance. With perseverance and adequate proctorship however, one cannot help but be impressed by the clarity and resolution afforded by this imaging modality. It is these images that have attracted considerable attention at cardiology conferences internationally and have helped instil OCT as the most sensitive intravascular imaging technique available today. The aim of this thesis was to evaluate the role of OCT in contemporary coronary intervention. Part 1 embraces the principles of the technique and the physical properties of OCT (chapter 2) and gives an insight into where OCT is placed compared to other intravascular imaging modalities (chapter 3). Despite the adoption of OCT in more and more catheterisation laboratories, little has been documented as to its safety, so, in chapter 4, we review the procedural safety of intracoronary OCT in a large group of patients across six leading European centres.

Incomplete Stent Apposition and Delayed Tissue Coverage Are More Frequent in Drug-Eluting Stents Implanted During Primary Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction Than in Drug-Eluting Stents Implanted for Stable/Unstable Angina. Insights From Optical Coherence Tomography (Article)

2009-05-01T00:00:00Z

Objectives: The aim of this study was to compare the frequency of incomplete stent apposition (ISA) and struts not covered by tissue at long-term follow-up (as assessed by optical coherence tomography [OCT]) in drug-eluting stents (DES) implanted during primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) versus DES implanted for unstable and stable angina. Background: Incomplete stent apposition and the absence of strut endothelialization might be linked to stent thrombosis. DES implanted for STEMI might have a higher risk of thrombosis. Methods: Consecutive patients in whom OCT was performed at least 6 months after DES implantation were included in the study. Stent struts were classified on the basis of the presence or absence of ISA and tissue coverage. Results: Forty-seven lesions in 43 patients (1,356 frames, 10,140 struts) were analyzed (49% stable angina, 17% unstable angina, 34% STEMI). Median follow-up time was 9 (range 7 to 72) months. Drug-eluting stents implanted during primary PCI presented ISA more often than DES implanted in stable/unstable angina patients (75% vs. 25.8%, p = 0.001). The frequency of uncovered struts was also higher in the STEMI group (93.8% vs. 67.7%, p = 0.048). On multivariate analysis, DES implantation in STEMI was the only independent predictor of ISA (odds ratio: 9.8, 95% confidence interval: 2.4 to 40.4, p = 0.002) and the presence of uncovered struts at follow-up (odds ratio: 9.5, 95% confidence interval: 1.0 to 90.3, p = 0.049). Conclusions: DES implanted for STEMI had a higher frequency of incompletely apposed struts and uncovered struts as assessed by OCT at follow-up. DES implantation during primary PCI in STEMI was an independent predictor of ISA and the presence of uncovered struts at follow-up.

In Vivo Assessment of High-Risk Coronary Plaques at Bifurcations With Combined Intravascular Ultrasound and Optical Coherence Tomography (Article)

2009-04-01T00:00:00Z

Objectives: This study sought to evaluate the in vivo frequency and distribution of high-risk plaques (i.e., necrotic core rich) at bifurcations using a combined plaque assessment with intravascular ultrasound-virtual histology (IVUS-VH) and optical coherence tomography (OCT). Background: Pathological examinations have shown that atherosclerotic plaque rich in necrotic core is prone to develop at bifurcations. High-risk plaque detection could be improved by the combined use of a technique able to detect necrotic core (IVUS-VH) and a high-resolution technique that allows the measurement of the fibrous cap thickness (OCT). Methods: From 30 patients imaged with IVUS-VH and OCT, 103 bifurcations were selected. The main branch was analyzed at the proximal rim of the ostium of the side branch, at the in-bifurcation segment and at the distal rim of the ostium of the side branch. Plaques with more than 10% confluent necrotic core by IVUS-VH were selected and classified as fibroatheroma (FA) or thin-cap fibroatheroma (TCFA) depending on the thickness of the fibrous cap by OCT (>65 or ≤65 μm for FA and TCFA, respectively). Results: Twenty-seven FA (26.2%) and 18 TCFA (17.4%) were found out of the 103 lesions studied. Overall the percentage of necrotic core decreases from proximal to distal rim (16.8% vs. 13.5% respectively, p = 0.01), whereas the cap thickness showed an inverse tendency (130 ± 105 μm vs. 151 ± 68 μm for proximal and distal rim, respectively, p = 0.05). The thin caps were more often located in the proximal rim (15 of 34, 44.1%), followed by the in-bifurcation segment (14 of 34, 41.2%), and were less frequent in the distal rim (5 of 34, 14.7%). Conclusions: The proximal rim of the ostium of the side branch has been identified as a region more likely to contain thin fibrous cap and a greater proportion of necrotic core.

Intracoronary optical coherence tomography and the evaluation of stents (Article)

2009-01-01T00:00:00Z

The application of optical coherence tomography to the cardiovascular system has led to intense interest, both clinically and also on the research front. Based on sound optical physics, intracoronary, in vivo imaging with high resolution (15 µm) has given unique insights into not only atherosclerotic plaques but also the tissue responses underlying stent implantation. This article will introduce the application of optical coherence tomography technology to coronary arteries, with particular reference to the evaluation of stents, and will also give a glimpse into current and future developments that will see optical coherence tomography remain a key tool in the armamentarium of researchers and interventional cardiologists alike

Assessment of Culprit and Remote Coronary Narrowings Using Optical Coherence Tomography With Long-Term Outcomes (Article)

2008-08-15T00:00:00Z

Much currently known information about vulnerable plaque stems from postmortem studies that identified several characteristics making them prone to rupture, including the presence of a thin fibrous cap and a large lipid core. This study used optical coherence tomography (OCT) to assess culprit and remote coronary narrowings and investigate whether intracoronary OCT in living patients was able to visualize morphologic features associated with vulnerable plaque in postmortem studies. Twenty-three patients successfully underwent OCT before percutaneous coronary intervention. The culprit lesion and mild to moderate coronary narrowings remote from the target stenosis were investigated. Using OCT, the culprit lesion was found to be fibrous in 39.1%, fibrocalcific in 34.4%, and lipid rich in 26.1% of cases. Two patients met criteria for thin-cap fibroatheroma (TCFA; defined as the presence of a signal-rich fibrous cap covering a signal-poor lipid/necrotic core with cap thickness <0.2 mm). Most plaques at remote segments were proximal to the culprit lesion (73.9%) and predominantly fibrous and lipid rich. OCT identified 7 TCFA lesions in 6 patients with a mean cap thickness of 0.19 ± 0.05 mm, extending for 103° ± 49° of the total vessel circumference. At 24 months of clinical follow-up, the only event occurred in a patient with in-stent restenosis who underwent repeated percutaneous revascularization. There were no clinically apparent plaque rupture-related events in the 6 patients found to have remote TCFA. This study showed that OCT can be safely applied to image beyond the culprit lesion and can detect in vivo morphologic features associated with plaque vulnerability using retrospective pathologic examination. In conclusion, detection of TCFA, particularly in stable patients, is desirable and may principally allow for early intervention and prevention of adverse events.

Optical coherence tomography assessment of vulnerable plaque rupture: Predilection for the plaque 'shoulder' (Article)

2008-08-01T00:00:00Z

A novel approach for quantitative analysis of intracoronary optical coherence tomography: High inter-observer agreement with computer-assisted contour detection (Article)

2008-08-01T00:00:00Z

Objective: This study aims to examine observer-related variability of quantitative optical coherence tomography (OCT) derived measurements from both in vitro and in vivo pullback data. Background: Intravascular OCT is a new imaging modality using infrared light and offering 10 times higher image resolution (15 μm) compared to intravascular ultrasound. The quantitative analysis of in vivo intracoronary OCT imaging is complicated by the presence of blood, motion artifacts and the large quantity of information that has to be processed. Methods: We developed a standardized, automated quantification process for intracoronary OCT pullback data with inter-observer variability assessed both in vitro by using postmortem human coronary arteries and in vivo by studying simple and complex coronary pathology and outcomes following stent implantation. The consensus between measurements by two observers was analyzed using the intraclass and interclass correlation coefficient and the reliability coefficients. Bland-Altman plots were generated to assess the relationship between variability and absolute measurements. Results: In vitro OCT assessment was performed in nine postmortem coronary arteries. The time needed for semiautomated contour detection of a 15-mm long coronary segment was ∼40 min. The absolute and relative difference between lumen area measurements derived from two observers was low [0.02 ± 0.10 mm2; (0.3 ± 0.5)% respectively] with excellent correlation confirmed by linear regression analysis (R2= 0.99; P < 0.001). Similarly, in vivo measurements demonstrated a high correlation with the main source of inter-observer variation occurring as a result of coronary dissection and motion artifact. The absolute and relative difference between measurements were 0.11 ± 0,33 mm2(1.57 ± 0.05)% for lumen area (R2= 0.98; P < 0.001), 0.17 ± 0.68 mm2(1.44 ± 0.08)% for stent area (R2= 0.94; P < 0.001), and 0.26 ± 0.72 mm2(14.05 ± 0.37)% for neointimal area (R2= 0.78; P < 0.001). Conclusions: Highly accurate computer-assisted quantitative analysis of intracoronary OCT pullbacks is feasible with low inter-observer variability. The presented approach allows for observer independent analysis of detailed vessel structures, and may be a valuable tool for future longitudinal studies incorporating OCT,

Optical Coherence Tomography Findings in Very Late (4 Years) Paclitaxel-Eluting Stent Thrombosis (Article)

2008-08-01T00:00:00Z