Coronary plaque composition as assessed by greyscale intravascular ultrasound and radiofrequency spectral data analysis

Objectives: (i) To explore the relation between greyscale intravascular ultrasound (IVUS) plaque qualitative classification and IVUS radiofrequency data (RFD) analysis tissue types; (ii) to evaluate if plaque composition as assessed by RFD analysis can be predicted by visual assessment of greyscale IVUS images. Methods: In 120 IVUS-RFD cross-sections, a sector of the plaque with homogenous tissue composition (e.g., fibrous, fibrofatty, necrotic core, and dense calcium) was selected. Two experienced observers analyzed twice the corresponding greyscale IVUS images to: (1) classify the selected sectors according to greyscale IVUS plaque type classification and (2) predict the tissue type expected in the sector by RFD analysis. Results: In the greyscale IVUS plaque type classification, the observers agreed in 90/120 sectors (κ = 0.64). Calcified, soft and mixed plaques by greyscale IVUS classification were mainly composed of dense calcium, fibrofatty, and necrotic core, respectively, in the RFD analysis. The plaques classified in greyscale IVUS as fibrous were actually fibrous tissue by IVUS RFD in only 30% of the cases. Overall, high interobserver variability in the prediction of RFD results by visual assessment of greyscale IVUS images (κ = 0.23 for observer 1 and 0.55 for observer 2) was found. Sens

Reproducibility of volumetric intravascular ultrasound radiofrequency-based analysis of coronary plaque composition in vivo

Intravascular ultrasound radiofrequency (RF-IVUS) data permit the analysis of coronary plaque composition in vivo and is used as an endpoint of ongoing pharmacological intervention trials. We assessed the reproducibility of volumetric RF-IVUS analyses in mild-to-moderately diseased atherosclerotic human coronary arteries in vivo. A total of 9,212 IVUS analyses on cross-sectional IVUS frames was performed to evaluate the reproducibility of volumetric RF-IVUS measurements in 33 coronary segments with a length of 27 ± 7 mm. For vessel, lumen, and plaque + media volume the relative measurement differences (P = NS for all) were (A = intraobserver comparison, same pullback) −0.40 ± 1.0%; −0.48 ± 1.4%; −0.35 ± 1.6%, (B = intraobserver comparison, repeated pullback) −0.42 ± 1.2%; −0.52 ± 1.8%; −0.43 ± 4.5% (C = interobserver comparison, same pullback) 0.71 ± 1.8%; 0.71 ± 2.2%, and 0.89 ± 5.0%, respectively. For fibrous, fibro-lipidic, calcium, and necrotic-core volumes the relative measurement differences (P = NS for all) were (A) 0.45 ± 2.1%; −1.12 ± 4.9%; −0.84 ± 2.1%; −0.22 ± 1.8%, (B) 1.40 ± 4.1%; 1.26 ± 6.7%; 2.66 ± 7.4%; 0.85 ± 4.4%, and (C) −1.60 ± 4.9%; 3.85 ± 8.2%; 1.66 ± 7.5%, and −1.58 ± 4.7%, respectively. Of note, necrotic-core volume showed on average the lowest measurement variability. Thus, in mild-to-moderate atherosclerotic coronary artery disease the reproducibility of volumetric compositional RF-IVUS measurements from the same pullback is relatively high, but lower than the reproducibility of geometrical IVUS measurements. Measurements from repeated pullbacks and by different observers show acceptable reproducibilities; the volumetric measurement of the necrotic-core shows on average the highest reproducibility of the compositional RF-IVUS measurement

Impact of analyzing less image frames per segment for radiofrequency-based volumetric intravascular ultrasound measurements in mild-to-moderate coronary atherosclerosis

Volumetric radiofrequency-based intravascular ultrasound (RF–IVUS) data of coronary segments are increasingly used as endpoints in serial trials of novel anti-atherosclerotic therapies. In a relatively time-consuming process, vessel and lumen contours are defined; these contours are first automatically detected, then visually checked, and finally (in most cases) manually edited to generate reliable volumetric data of vessel geometry and plaque composition. Reduction in number of cross-sectional images for volumetric analysis could save analysis time but may also increase measurement variability of volumetric data. To assess whether a 50% reduction in number of frames per segment (every second frame) alters the reproducibility of volumetric measurements, we performed repeated RF–IVUS analyses of 15 coronary segments with mild-to-moderate atherosclerosis (20.2 ± 0.2 mm-long segments with 46 ± 13% plaque burden). Volumes were calculated based on a total of 731 image frames. Reducing the number of cross-sectional image frames for volumetric measurements saved analysis time (38 ± 9 vs. 68 ± 17 min/segment; P < 0.0001) and resulted for only a few parameters in (borderline) significant but mild differences versus measurements based on all frames (fibrous volume, P < 0.05; necrotic-core volume, P = 0.07). Compared to the intra-observer variability, there was a mild increase in measurement variability for most geometrical and compositional volumetric RF–IVUS parameters. In RF–IVUS studies of mild-to-moderate coronary disease, analyzing less image frames saved analysis time, left most volumetric parameters greatly unaffected, and resulted in a no more than mild increase in measurement variability of volumetric data

Impact of analyzing fewer image frames per segment during offline volumetric radiofrequency-based intravascular ultrasound measurements of target lesions prior to percutaneous coronary interventions

In the present study, we evaluated the impact of a 50% reduction in number of image frames (every second frame) on the analysis time and variability of offline volumetric radiofrequency-based intravascular ultrasound (RF-IVUS) measurements in target lesions prior to percutaneous coronary interventions (PCI). Volumetric RF-IVUS data of vessel geometry and plaque composition are generally obtained by a semi-automated analysis process that includes time-consuming manual contour editing. A reduction in the number of frames used for volumetric analysis may speed up the analysis, but could increase measurement variability. We repeatedly performed offline volumetric analyses in RF-IVUS image sets of 20 mm-long coronary segments that contained 30 de novo lesions prior to PCI. A 50% reduction in frames decreased the analysis time significantly (from 57.5 ± 7.3 to 35.7 ± 3.7 min; P < 0.0001) while geometric and compositional RF-IVUS measurements did not differ significantly from measurements obtained from all frames. The variability between measurements on the reduced number of frames versus all frames was comparable to the intra-observer measurement variability. In target lesions prior to PCI, offline volumetric RF-IVUS analyses can be performed using a reduced number of image frames (every second frame). This reduces the time of analysis without substantially increasing measurement variability

Interstudy reproducibility of the second generation, Fourier domain optical coherence tomography in patients with coronary artery disease and comparison with intravascular ultrasound: a study applying automated contour detection

Recently, Fourier domain OCT (FD-OCT) has been introduced for clinical use. This approach allows in vivo, high resolution (15 micron) imaging with very fast data acquisition, however, it requires brief flushing of the lumen during imaging. The reproducibility of such fast data acquisition under intracoronary flush application is poorly understood. To assess the inter-study variability of FD-OCT and to compare lumen morphometry to the established invasive imaging method, IVUS. 18 consecutive patients with coronary artery disease scheduled for PCI were included. In each target vessel a FD-OCT pullback (MGH system, light source 1,310 nm, 105 fps, pullback speed 20 mm/s) was acquired during brief (3 s) injection of X-ray contrast (flow 3 ml/s) through the guiding catheter. A second pullback was repeated under the same conditions after re-introduction of the FD OCT catheter into the coronary artery. IVUS and OCT imaging was performed in random order. FD-OCT and IVUS pullback data were analyzed using a recently developed software employing semi automated lumen contour and stent strut detection algorithms. Corresponding ROI were matched based on anatomical landmarks such as side branches and/or stent edges. Inter-study variability is presented as the absolute difference between the two pullbacks. FD-OCT showed remarkably good reproducibility. Inter-study variability in native vessels (cohort A) was very low for mean and minimal luminal area (0.10 ± 0.38, 0.19 ± 0.57 mm[superscript 2], respectively). Likewise inter-study variability was very low in stented coronary segments (cohort B) for mean lumen, mean stent, minimal luminal and minimal stent area (0.06 ± 0.08, 0.07 ± 0.10, 0.04 ± 0.09, 0.04 ± 0.10 mm[superscript 2], respectively). Comparison to IVUS morphometry revealed no significant differences. The differences between both imaging methods, OCT and IVUS, were very low for mean lumen, mean stent, minimal luminal and minimal stent area (0.10 ± 0.45, 0.10 ± 0.36, 0.26 ± 0.54, 0.05 ± 0.47 mm[superscript 2], respectively). FD-OCT shows excellent reproducibility and very low inter-study variability in both, native and stented coronary segments. No significant differences in quantitative lumen morphometry were observed between FD-OCT and IVUS. Evaluating these results suggest that FD-OCT is a reliable imaging tool to apply in longitudinal coronary artery disease studie

Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

Intravascular ultrasound (IVUS) is an invasive modality which provides cross-sectional images of a coronary artery. In these images both the lumen and outer vessel wall can be identified and accurate estimations of their dimensions and of the plaque burden can be obtained. In addition, further processing of the IVUS backscatter signal helps in the characterization of the type of the plaque and thus it has been used to study the natural history of the atherosclerotic evolution. On the other hand its indigenous limitations do not allow IVUS to assess accurately stent struts coverage, existence of thrombus or exact site of plaque rupture and to identify some of the features associated with increased plaque vulnerability. In order this information to be obtained, other modalities such as optical coherence tomography, angioscopy, near infrared spectroscopy and intravascular magnetic resonance imaging have either been utilized or are under evaluation. The aim of this review article is to present the current utilities of IVUS in research and to discuss its advantages and disadvantages over the other imaging techniques

LONG TERM EFFECT OF PERINDOPRIL ON CORONARY ATHEROSCLEROSIS PROGRESSION (FROM THE PERINDOPRIL'S PROSPECTIVE EFFECT ON CORONARY ATHEROSCLEROSIS BY ANGIOGRAPHY AND INTRAVASCULAR ULTRASOUND EVALUATION [PERSPECTIVE] STUDY).

The multicenter EUROPA trial of 12,218 patients showed that perindopril decreased adverse clinical events in patients with established coronary heart disease. The PERSPECTIVE study, a substudy of the EUROPA trial, evaluated the effect of perindopril on coronary plaque progression as assessed by quantitative coronary angiography and intravascular ultrasound (IVUS). In total 244 patients (mean age 57 years, 81% men) were included. Evaluable paired quantitative coronary angiograms were obtained from 96 patients randomized to perindopril and from 98 patients to placebo. Concomitant treatment at baseline consisted of aspirin (90%), lipid-lowering agents (70%), and blockers (60%). The primary and secondary end point was the difference of minimum and mean lumen diameters (quantitative coronary angiography) or mean plaque cross-sectional area (IVUS) measured at baseline and 3-year follow-up between the perindopril and placebo groups. After a median follow-up of 3.0 years (range 1.9 to 4.1), no differences in change in quantitative coronary angiographic or IVUS measurements were detected between the perindopril and placebo groups (minimum and mean luminal diameters 0.07 0.4 vs 0.02 0.4 mm, p 0.34; mean luminal diameter 0.05 0.2 vs 0.05 0.3 mm, p 0.89; mean plaque crosssectional area 0.18 1.2 vs 0.02 1.2 mm2, p 0.48). In conclusion, we found no progression in coronary artery disease by quantitative coronary angiography and IVUS with long-term administration of perindopril or placebo, possibly because most patients were on concomitant treatment with a statin

Clinical expert consensus document on standards for acquisition, measurement and reporting of intravascular ultrasound regression/progression studies

Atherosclerotic cardiovascular disease is a leading cause of morbidity and mortality despite the widespread use of established medical therapies. This has prompted the search to identify new therapeutic approaches to achieve more effective prevention of cardiovascular events. Considerable interest has focused on the role of surrogate markers of therapeutic efficacy in the early evaluation of novel anti-atherosclerotic therapies. Monitoring changes in the extent of coronary atherosclerosis with intravascular ultrasound (IVUS) has been increasingly employed in clinical trials to assess progression and regression of atherosclerosis. This is based on the pivotal role that atherosclerotic plaque plays in the natural history of cardiovascular disease and the acceptance of validated arterial imaging approaches including coronary angiography and carotid intimal-medial thickness by regulatory authorities. The ability to generate high-resolution imaging of the entire thickness of the coronary artery wall permits evaluation of the entire burden of atherosclerotic plaque. In order to understand the differences, similarities, limitations and pitfalls of the IVUS technique among different academic core laboratories, a number of meetings of representatives from these groups were convened in 2007 and 2008. This document is result of those IVUS methodology meetings that assembled experts from core laboratories to discuss standards for image acquisition, definitions, criteria, analyses, and primary and secondary endpoints