IVUS-guided versus OCT-guided PCI among patients presenting with acute coronary syndrome

BACKGROUND

Intravascular imaging modalities such as intravascular ultrasound (IVUS) and, more recently, optical coherence tomography (OCT) improved the visualization of coronary anatomy and plaque pathology. We aimed to compare the procedural and short-term outcomes between IVUS-guided and OCT-guided percutaneous coronary interventions (PCIs) in patients with acute coronary syndrome (ACS).

METHODS

In the present retrospective study, we reviewed the data of 50 patients who had IVUS-guided PCI and 50 patients who had OCT-guided PCI for ACS between January 2020 and June 2021. Intravascular imaging was done before and after stenting. Both groups were compared in terms of minimal luminal area (MLA), stent dimensions, final minimal stent area (MSA) and stent expansion as well as negative angiographic outcomes. Patients were followed for six months to record major adverse cardiac events (MACE).

RESULTS

The patients' mean age was 57 ± 13 years with male predominance (78%). The radiation time and dose were significantly higher among IVUS group. Pre-stenting MLA was significantly higher in IVUS group (2.63 mm vs. 2.22 mm in OCT, P = 0.013). Stent expansion was significantly higher among OCT group (97% vs. 93% in IVUS group, P = 0.001) with no significant difference between both groups regarding MSA [mm²] (8.88 ± 2.87 in IVUS vs. 8.1 ± 2.76 in OCT, P = 0.169). No significant difference between both groups was noted regarding contrast volume, edge dissection, tissue prolapse, and no reflow. The rates of six-month MACE were significantly higher in the IVUS group.

CONCLUSIONS

OCT-guided PCI in ACS is safe and is associated with similar MSA to that of IVUS-guided PCI. Future randomized trials are needed to confirm these findings.

Validation of a semi-automatic software for optical coherence tomography - analysis in heart transplanted patients

Optical Coherence Tomography (OCT) is an intravascular imaging modality enabling detailed evaluation of cardiac allograft vasculopathy (CAV) after heart transplantation (HTx). However, its clinical application remains hampered by time-consuming manual quantitative analysis. We aimed to validate a semi-automated quantitative OCT analysis software (Iowa Coronary Wall Analyzer, ICWA-OCT) to improve OCT-analysis in HTx patients. 23 patients underwent OCT evaluation of all three major coronary arteries at 3 months (3M) and 12 months (12M) after HTx. We analyzed OCT recordings using the semiautomatic software and compared results with measurements from a validated manual software. For semi-automated analysis, 31,228 frames from 114 vessels were available. The validation was based on a subset of 4287 matched frames. We applied mixed model statistics to accommodate the multilevel data structure with method as a fixed effect. Lumen (minimum, mean, maximum) and media (mean, maximum) metrics showed no significant differences. Mean and maximum intima area were underestimated by the semi-automated method (β-methodmean = - 0.289 mm2, p < 0.01; β-methodmax = - 0.695 mm2, p < 0.01). Bland-Altman analyses showed increasing semi-automatic underestimation of intima measurements with increasing intimal extent. Comparing 3M to 12M progression between methods, mean intimal area showed minor underestimation (β-methodmean = - 1.03 mm2, p = 0.04). Lumen and media metrics showed excellent agreement between the manual and semi-automated method. Intima metrics and progressions from 3M to 12M were slightly underestimated by the semi-automated OCT software with unknown clinical relevance. The semi-automated software has the future potential to provide robust and time-saving evaluation of CAV progression.

Plaque burden estimated from optical coherence tomography with deep learning: In vivo validation using co-registered intravascular ultrasound

OBJECTIVES

The objective of the present study was to compare plaque burden (PB) calculated from optical coherence tomography (OCT) using deep learning (DL) with PB derived from co-registered intravascular ultrasound (IVUS).

BACKGROUND

A DL algorithm was developed for automated plaque characterization and PB quantification from OCT images. However, the performance of this algorithm for PB quantification has not been validated.

METHODS

Five-year follow-up OCT and IVUS images from 15 patients implanted with bioresorbable vascular scaffold (BVS) at baseline were analyzed. Precise co-registration for 72 anatomical slices was achieved utilizing unique BVS radiopaque markers. PB derived from OCT DL and IVUS were compared. OCT cross-sections were divided into four subgroups with different media visibility level. The impact of media visibility on the numerical difference between OCT-derived and IVUS-derived PB was investigated. The stent sizes selected by OCT DL and IVUS were compared.

RESULTS

Sixty-four paired OCT and IVUS cross-sections were compared. OCT DL showed good concordance with IVUS for PB assessment (ICC = 0.81, difference = -3.53 ± 6.17%, p < 0.001). The numerical difference between OCT DL-derived PB and IVUS-derived PB was not substantially impacted by missing segments of media visualization (p = 0.21). OCT DL showed a diagnostic accuracy of 92% in identifying PB > 65%. The stent sizes selected by OCT DL were smaller compared to the ones selected by IVUS (difference = 0.30 ± 0.34 mm, p < 0.001).

CONCLUSIONS

The DL algorithm provides a feasible and reliable method for automated PB estimation from OCT, irrespective of media visibility. OCT DL showed good diagnostic accuracy in identifying PB > 65%, revealing its potential to complement conventional OCT imaging.

Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis

Aims

The aim of this study was to assess the safety and diagnostic efficacy of frequency-domain optical coherence tomography (FD-OCT) in identifying functional severity of the left main coronary artery (LM) stenosis determined by fractional flow reserve (FFR).

Methods and Results

101 patients with LM lesion (20-70% diameter stenosis angiographically) underwent FFR measurement and FD-OCT imaging of the LM. The following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, and % diameter stenosis. The LM lesions were analyzable by FD-OCT in 88/101 (87.1%) patients. FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT-derived LM lumen parameters. An MLA cutoff value of 5.38 mm² had the highest sensitivity and specificity of 82% and 81%, respectively, followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) and AS of 60% (sensitivity 72%, specificity 72%) for predicting FFR <0.80.

Conclusions

FD-OCT is a safe and feasible imaging technique for the assessment of LM stenosis. An FD-OCT-derived MLA of ≤5.38 mm² strongly predicts the functional severity of an LM lesion.

Clinical impact of a new optical coherence tomography-derived volumetric method for evaluating stent expansion

The aim of this study was to investigate the impact of a new optical coherence tomography (OCT)-derived volumetric method for stent expansion (new-OCT method) to predict the target lesion revascularization (TLR) and compare the expansion findings between this new method and the conventional method because, in the real world, there are few clinical data on the new-OCT-method for stent expansion. One hundred forty lesions in 135 patients who underwent OCT-guided percutaneous coronary intervention were enrolled. We compared the new-OCT-method and conventional method to predict the TLR at 1 year. A total of 7 lesions (5.0% of treated lesions) in 6 patients experienced TLR during 1 year of follow up. The minimum expansion index (MEI) using the new-OCT method was significantly lower in the TLR group than non-TLR (60.0% vs. 77.0%; p < 0.001) while the conventional method for assessing stent expansion did not show a statistically significant difference between the two groups (71.3% and 79.7%; p = 0.118). The univariate analysis showed that the stent length, minimum stent area, minimum lumen area, MEI, and renal insufficiency/failure, were significant predictors of a 1-year TLR. The multivariate model identified the stent length, MEI, and renal insufficiency/failure as the independent predictors of TLR and the value of the MEI was the only predictor in the OCT findings. The new OCT-derived volumetric method for stent expansion is superior to the conventional method for predicting the TLR at 1 year. The MEI may be the most practical and efficient way to estimate stent under-expansion.

Optical coherence tomography versus intravascular ultrasound in patients with myocardial infarction: a diagnostic performance study of pre-percutaneous coronary interventions

Accurate coronary measurements are important in guiding percutaneous coronary intervention. Intravascular ultrasound is a widely accepted diagnostic modality for coronary measurement before percutaneous coronary intervention. The spatial resolution of optical coherence tomography is 10 times larger than that of intravascular ultrasound. The objective of the study was to compare quantitative and qualitative parameters of frequency domain optical coherence tomography (FDOCT) with those of intravascular ultrasound and coronary angiography in patients with acute myocardial infarction. Diagnostic parameters of coronary angiography, intravascular ultrasound, and FDOCT of 250 patients with coronary artery disease who required admission diagnosis were included in the analyses. Minimum lumen diameter detected by FDOCT was larger than that detected by quantitative coronary angiography (2.11±0.1 vs 1.89±0.09 mm, P<0.0001, q=34.67) but smaller than that detected by intravascular ultrasound (2.11±0.1 vs 2.19±0.11 mm, P<0.0001, q=12.61). Minimum lumen area detected by FDOCT was smaller than that detected by intravascular ultrasound (3.41±0.01 vs 3.69±0.01 mm², P<0.0001). FDOCT detected higher numbers of thrombus, tissue protrusion, dissection, and incomplete stent apposition than those detected by intravascular ultrasound (P<0.0001 for all). More accurate and sensitive results of the coronary lumen can be detected by FDOCT than coronary angiography and intravascular ultrasound (level of evidence: III).

New insight to estimate under-expansion after stent implantation on bifurcation lesions using optical coherence tomography

Optical coherence tomography (OCT) allows full volumetric segmentation of the lumen. However, for the estimation of stent under-expansion we still rely on the conventional method (CM) of single cross-sectional narrowing compared with reference vessel, likely masking true lesion significance, especially for bifurcations and tapered vessels. We, therefore, suggest a novel concept of volumetric metrics that take into account vessel tapering and major side branches and is capable of obtaining ideal lumen area for every frame of the stent by OCT. Forty-four patients with bifurcation lesions were enrolled. In volumetric metrics, expansion index was calculated as [(actual lumen area/ideal lumen area) × 100] in all frames. While minimum expansion index (MEI) was often located in the proximal segment to the major side branch, minimum stent area (MSA) by CM was frequently located in the distal segment (p < 0.001). Furthermore, the frequency of the under-expansion was significantly greater in newly metrics compared with CM [21 (47.7%) and 11 (25.0%), p = 0.045]. New metrics changed the presence of the under-expansion in 40.9% (18/44) of patients and the locations of MEI and MSA were different in 72.7% (32/44) of cases. Volumetric assessment enables to more accurately assess stent under-expansion.

Bioresorbable Scaffolds for Coronary Stenosis: When and How Based Upon Current Studies

PURPOSE OF REVIEW

First-generation bioresorbable scaffolds (BRS), largely represented by the poly-l-lactic acid (PLLA) ABSORB (Abbott Vascular, Temecula, Illinois, US), have demonstrated, in low to moderate lesion complexity, similar efficacy to current generation metallic drug-eluting stents. However, a trend toward more device thrombosis has been observed, especially when the scaffolds are used in off-label situations. In this review, we address the most relevant drawbacks of these devices and, based on the available scientific data, we visit the scenarios where there is more uncertainty about their indication, trying to identify the lesions/patients to whom this technology should be voided at its current stage of development.

RECENT FINDINGS

Based on available data from randomized trials and observational real world registries, the use of first generation BRS has been associated with a trend to higher acute/subacute thrombosis rate, which might be partially explained by the peculiarities related to their deployment technique, such as the need for precise vessel sizing and caution on post-dilation. Special attention should be paid when using these devices to treat small coronary arteries (<2.5 mm), long lesions requiring overlapping, and patients with acute coronary syndrome, in particular those with ST-segment elevation myocardial infarction (STEMI). Finally, the role of these devices is still uncertain in more complex lesion anatomies such as bifurcations, ostial lesions, etc. Although based on attractive clinical premises, the current indications of BRS are still limited by significant drawbacks observed in the first generation of these devices. Of note, new generation scaffolds are currently in preclinical and clinical evaluation and present features that might surpass most of these limitations.

Role of invasive imaging in acute and long-term assessment of bioresorbable scaffold technology

Fully bioresorbable scaffolds (BRS) represent a novel approach for the percutaneous treatment of coronary artery stenosis, providing temporary vessel scaffolding with drug-eluting capability during the restenosis-prone phase of the vascular healing. Beyond this initial critical period, when mechanical scaffolding support is no longer necessary, the device is bioresorbed, restoring the normal vascular physiology with the aim to eliminate the long-term safety concerns related to permanent metallic implants. Nonetheless, current BRS technology suffers from limited mechanical properties as compared to available metallic platforms, requiring careful attention to lesion preparation, accurate vessel sizing, and implantation technique. Intravascular imaging has played an important role in providing knowledge on the acute effects after BRS deployment, and it helped refine the current technique of BRS implantation. In addition, extensive work with multiple intravascular imaging modalities have also contributed to the understanding of the unique dynamic vascular changes that are experienced in the treated segment from post-implantation up to complete device bioresorption. In this manuscript, we review the role of invasive imaging modalities-from angiography to sound- and light-based techniques-to guide BRS implantation procedures, to assess its acute results postimplantation, and the changes experienced in the long-term until complete bioresorption has ensued. © 2016 Wiley Periodicals, Inc.

Optical coherence tomography versus intravascular ultrasound to evaluate stent implantation in patients with calcific coronary artery disease

AIMS

Stent underexpansion and malapposition are associated with adverse outcomes following percutaneous coronary intervention, but detection and treatment can be challenging in the presence of extensive coronary artery calcification. Frequency domain optical coherence tomography (FD-OCT) is a novel intravascular imaging technique with greater spatial resolution than intravascular ultrasound (IVUS) but its role in the presence of extensive coronary calcification remains unclear. We sought to determine the utility of FD-OCT compared to IVUS imaging to guide percutaneous coronary intervention in patients with severe calcific coronary artery disease.

METHODS

18 matched IVUS and FD-OCT examinations were evaluated following coronary stent implantation in 12 patients (10 male; mean age 70±7 years) undergoing rotational atherectomy for symptomatic calcific coronary artery disease.

RESULTS

In-stent luminal areas were smaller (minimum in-stent area 6.77±2.18 vs 7.19±2.62 mm(2), p<0.05), while reference lumen dimensions were similar with FD-OCT compared with IVUS. Stent malapposition was detected in all patients by FD-OCT and in 10 patients by IVUS. The extent of stent malapposition detected was greater (20% vs 6%, p<0.001) with FD-OCT compared to IVUS. Postdilation increased the in-stent luminal area (minimum in-stent area: 8.15±1.90 vs 7.30±1.62 mm(2), p<0.05) and reduced the extent of stent malapposition (19% vs 34%, p<0.005) when assessed by FD-OCT, but not IVUS.

CONCLUSIONS

Acute stent malapposition occurs frequently in patients with calcific coronary disease undergoing rotational atherectomy and stent implantation. In the presence of extensive coronary artery calcification, FD-OCT affords enhanced stent visualisation and detection of malapposition, facilitating improved postdilation stent apposition and minimal luminal areas.

TRIAL REGISTRATION NUMBER

NCT02065102.

Changes in the reference lumen size of target lesions before and after coronary stent implantation: Evaluation with frequency domain optical coherence tomography

Objective

In optical coherence tomography (OCT)-guided percutaneous coronary intervention (PCI), stent size is usually determined according to the pre-PCI lumen size of either the distal or proximal reference site. However, the effect of the OCT imaging catheter crossing the target lesion on the reference lumen measurements has not been studied. We evaluated changes in the reference lumen size before and after PCI using frequency domain OCT.

Methods

For 100 consecutive patients with PCI, mean lumen diameter (LD) and lumen area (LA) were measured at the proximal and distal reference sites before and after coronary stent implantation with OCT.

Results

Mean LD and LA of the distal reference site were significantly increased after PCI with stent implantation (2.57 ± 0.6 to 2.62 ± 0.64 mm, p < 0.01 and 5.20 ± 2.66 to 5.41 ± 2.54 mm², p < 0.01, respectively). By contrast, these indices at the proximal reference site were significantly decreased. ROC curve analysis selected MLA of 1.50 mm² as the best cutoff value for changes in mean LD. Distal mean LD was markedly increased after PCI in lesions with MLA < 1.50 mm (2.28 ± 0.48 to 2.40 ± 0.17 mm, P < 0.001), but did not change in lesions with MLA > 1.50 mm². Tissue characteristics were not correlated with changes in reference lumen size.

Conclusions

When we select the stent size during OCT-guided PCI, we need to pay attention to the decrease in the luminal measurement of the reference sites, especially in lesions with tight stenosis.

Quantitative precision of optical frequency domain imaging: direct comparison with frequency domain optical coherence tomography and intravascular ultrasound

No systematic validation study is available with optical frequency domain imaging (OFDI), directly compared with frequency domain optical coherence tomography (FD-OCT) and intravascular ultrasound (IVUS). Controversy also remains about the impact of different stent contour tracing methods by OFDI/FD-OCT. In vitro: coronary phantom models (1.51–5.04 mm) were imaged with OFDI, FD-OCT, and IVUS, demonstrating excellent quantitative precision with a slight overestimation of mean lumen diameter (difference 0.01–0.02 mm). In vivo: corresponding 64 OFDI/IVUS images of stented coronary segments from 20 swines were analyzed. Minimum lumen area by OFDI was larger than IVUS at baseline (P < 0.001), whereas it was smaller than IVUS at follow-up. When stent was traced at leading edges of struts by OFDI, minimum stent area was similar between OFDI and IVUS (P = 0.60). When traced at the highest intensity points of struts by OFDI, it was significantly larger in OFDI than in IVUS (P < 0.001). Three modalities have clinically acceptable precision across the wide range of lumen diameters. In vivo measurements by OFDI and IVUS could slightly be discrepant depending on the parameters and time points. In stent assessment by OFDI, the 2 methods led to a small but systematic difference; therefore, consistency in methodology is advised for comparative studies.

Assessment and Quantitation of Stent Results by Intracoronary Optical Coherence Tomography

Optical coherence tomography evaluation of poststent results includes stent expansion as the absolute minimum stent area ratio by comparing the minimum stent area with the proximal and distal reference lumen areas or mean stent area defined as the total stent volume divided by the analyzed stent length; stent strut malapposition defined when the distance from the center of the blooming artifact and the surface of plaque is greater than the sum of stent thickness and polymer thickness; tissue protrusion through the stent struts; semiquantitative residual thrombus evaluation; and stent edge dissection.

Optical coherence tomography versus intravascular ultrasound in the evaluation of observer variability and reliability in the assessment of stent deployment: the OCTIVUS study

OBJECTIVES

To compare the variability in the assessment of coronary stents among interventional cardiologists (readers) using optical coherence tomography (OCT) and intravascular ultrasound (IVUS).

BACKGROUND

IVUS is established and validated in the evaluation of coronary stent. For cardiologists without core lab expertise, the utility of IVUS is limited by image quality. OCT yields higher image resolution; however, the consistency with which these readers interpret OCT images has not been fully evaluated or compared with IVUS.

METHODS

OCT and IVUS image sets (five pairs) obtained after stent placement were reviewed by readers with clinical experience in both modalities. Parameters assessed included stent expansion and symmetry, reference vessel and in-stent cross-sectional area (CSA) and diameter, and stent strut apposition as well as Multicenter Ultrasound Stenting in Coronaries criteria. These interpretations were compared with core lab readings and examined for interobserver variability.

RESULTS

The interobserver variability for measurement of in-stent CSA was 1.34 mm(2) using IVUS compared with 0.85 mm(2) using OCT (P = 0.024). Variation in the deviation from core lab measurement of in-stent CSA for IVUS was 1.48 mm(2) compared with 0.87 mm(2) for OCT (P = 0.042). The interobserver agreement for obtaining the Multicenter Ultrasound Stenting in Coronaries criteria using IVUS was 80.4% compared with 81.1% using OCT (P = 0.78). Compared with the corelab measurement, the readers obtained an agreement of 72.7% using IVUS vs. 67.3% using OCT (P = 0.43).

CONCLUSION

In the assessment of deployed coronary stents by practicing cardiologists, OCT images are interpreted more consistently compared with IVUS and can be used to assess stent deployment using IVUS-validated metrics.

Fully automated side branch detection in intravascular optical coherence tomography pullback runs

Side branches in the atherosclerotic lesion region are important as they highly influence the treatment strategy selection and optimization. Moreover, they are reliable landmarks for image registration. By providing high resolution delineation of coronary morphology, intravascular optical coherence tomography (IVOCT) has been increasingly used for side branch analysis. This paper presents a fully automated method to detect side branches in IVOCT images, which relies on precise segmentation of the imaging catheter, the protective sheath, the guide wire and the lumen. 25 in-vivo data sets were used for validation. The intraclass correlation coefficient between the algorithmic results and manual delineations for the imaging catheter, the protective sheath and the lumen contour positions was 0.997, 0.949 and 0.974, respectively. All the guide wires were detected correctly and the Dice's coefficient of the shadow regions behind the guide wire was 0.97. 94.0% of 82 side branches were detected with 5.0% false positives and the Dice's coefficient of the side branch size was 0.85. In conclusion, the presented method has been demonstrated to be accurate and robust for side branch analysis.

Variations in optical coherence tomography resolution and uniformity: a multi-system performance comparison

Point spread function (PSF) phantoms based on unstructured distributions of sub-resolution particles in a transparent matrix have been demonstrated as a useful tool for evaluating resolution and its spatial variation across image volumes in optical coherence tomography (OCT) systems. Measurements based on PSF phantoms have the potential to become a standard test method for consistent, objective and quantitative inter-comparison of OCT system performance. Towards this end, we have evaluated three PSF phantoms and investigated their ability to compare the performance of four OCT systems. The phantoms are based on 260-nm-diameter gold nanoshells, 400-nm-diameter iron oxide particles and 1.5-micron-diameter silica particles. The OCT systems included spectral-domain and swept source systems in free-beam geometries as well as a time-domain system in both free-beam and fiberoptic probe geometries. Results indicated that iron oxide particles and gold nanoshells were most effective for measuring spatial variations in the magnitude and shape of PSFs across the image volume. The intensity of individual particles was also used to evaluate spatial variations in signal intensity uniformity. Significant system-to-system differences in resolution and signal intensity and their spatial variation were readily quantified. The phantoms proved useful for identification and characterization of irregularities such as astigmatism. Our multi-system results provide evidence of the practical utility of PSF-phantom-based test methods for quantitative inter-comparison of OCT system resolution and signal uniformity.

Comparison of longitudinal geometric measurement in human coronary arteries between frequency-domain optical coherence tomography and intravascular ultrasound

Previous studies have demonstrated the higher accuracy of frequency-domain optical coherence tomography (FD-OCT) for quantitative measurements in comparison with intravascular ultrasound (IVUS). However, those analyses were based on the cross-sectional images. The aim of this study was to assess the accuracy of FD-OCT for longitudinal geometric measurements of coronary arteries in comparison with IVUS. Between October 2011 and March 2012, we performed prospective FD-OCT and IVUS examinations in consecutive 77 patients who underwent percutaneous coronary intervention with single stent. Regression analysis and Bland-Altman analysis revealed an excellent correlation between the FD-OCT-measured stent lengths and IVUS-measured stent lengths (r = 0.986, p < 0.001; mean difference = -0.51 mm). There was an excellent agreement between the actual stent lengths and the FD-OCT-measured stent lengths (r = 0.993, p < 0.001) as well as between the actual stent lengths and the IVUS-measured stent lengths (r = 0.981, p < 0.001). The difference between the actual stent lengths and the FD-OCT-measured stent lengths was significantly smaller than that between the actual stent lengths and the IVUS-measured stent lengths (0.15 ± 0.68 vs. 0.70 ± 1.15 mm, p < 0.001). Both FD-OCT (mean difference = -0.04 and -0.04 mm, respectively) and IVUS (mean difference = -0.06 and -0.06 mm, respectively) showed an excellent intra-observer and inter-observer reproducibility for the stent length measurements. In conclusion, FD-OCT provides accurate longitudinal measurement with excellent intra-observer and inter-observer reproducibility. FD-OCT might be a reliable technique for longitudinal geometric measurement in human coronary arteries.

Optical coherence tomography versus intravascular ultrasound to evaluate coronary artery disease and percutaneous coronary intervention

OBJECTIVES

We compared intravascular ultrasound (IVUS) and 2 different generations of optical coherence tomography (OCT)-time-domain OCT (TD-OCT) and frequency-domain OCT (FD-OCT)-for the assessment of coronary disease and percutaneous coronary intervention (PCI) using stents.

BACKGROUND

OCT is a promising light-based intravascular imaging modality with higher resolution than IVUS. However, the paucity of data on OCT image quantification has limited its application in clinical practice.

METHODS

A total of 227 matched OCT and IVUS pull backs were studied. One hundred FD-OCT and IVUS pull backs in nonstented (n = 56) and stented (n = 44) vessels were compared. Additionally, 127 matched TD-OCT and IVUS images were compared in stented vessels.

RESULTS

FD-OCT depicted more severe native coronary disease than IVUS; minimal lumen area (MLA) was 2.33 ± 1.56 mm(2) versus 3.32 ± 1.92 mm(2), respectively (p < 0.001). Reference vessel dimensions were equivalent between FD-OCT and IVUS in both native and stented coronaries, but TD-OCT detected smaller reference lumen size compared with IVUS. Immediately post-PCI, in-stent MLAs were similar between FD-OCT and IVUS, but at follow-up, both FD-OCT and TD-OCT detected smaller MLAs than did IVUS, likely due to better detection of neointimal hyperplasia (NIH). Post-PCI malapposition and tissue prolapse were more frequently identified by FD-OCT.

CONCLUSIONS

FD-OCT generates similar reference lumen dimensions but higher degrees of disease severity and NIH, as well as better detection of malapposition and tissue prolapse compared with IVUS. First-generation TD-OCT was associated with smaller reference vessel dimensions compared with IVUS.

OCT compared with IVUS in a coronary lesion assessment: the OPUS-CLASS study

OBJECTIVES

The aim of this study was to investigate the reliability of frequency domain optical coherence tomography (FD-OCT) for coronary measurements compared with quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS).

BACKGROUND

Accurate luminal measurement is expected in FD-OCT because this technology offers high resolution and excellent contrast between lumen and vessel wall.

METHODS

In 5 medical centers, 100 patients with coronary artery disease were prospectively studied by using angiography, FD-OCT, and IVUS. In addition, 5 phantom models of known lumen dimensions (lumen diameter 3.08 mm; lumen area 7.45 mm(2)) were examined using FD-OCT and IVUS. Quantitative image analyses of the coronary arteries and phantom models were performed by an independent core laboratory.

RESULTS

In the clinical study, the mean minimum lumen diameter measured by QCA was significantly smaller than that measured by FD-OCT (1.81 ± 0.72 mm vs. 1.91 ± 0.69 mm; p < 0.001) and the minimum lumen diameter measured by IVUS was significantly greater than that measured by FD-OCT (2.09 ± 0.60 mm vs. 1.91 ± 0.69 mm; p < 0.001). The minimum lumen area measured by IVUS was significantly greater than that by FD-OCT (3.68 ± 2.06 mm(2) vs. 3.27 ± 2.22 mm(2); p < 0.001), although a significant correlation was observed between the 2 imaging techniques (r = 0.95, p < 0.001; mean difference 0.41 mm(2)). Both FD-OCT and IVUS exhibited good interobserver reproducibility, but the root-mean-squared deviation between measurements was approximately twice as high for the IVUS measurements compared with the FD-OCT measurements (0.32 mm(2) vs. 0.16 mm(2)). In a phantom model, the mean lumen area according to FD-OCT was equal to the actual lumen area of the phantom model, with low SD; IVUS overestimated the lumen area and was less reproducible than FD-OCT (8.03 ± 0.58 mm(2) vs. 7.45 ± 0.17 mm(2); p < 0.001).

CONCLUSIONS

The results of this prospective multicenter study demonstrate that FD-OCT provides accurate and reproducible quantitative measurements of coronary dimensions in the clinical setting.

Volumetric assessment of lesion severity with optical coherence tomography: relationship with fractional flow

AIMS

Frequency-domain optical coherence tomography (FD-OCT) provides a rapid tomographic scan of a coronary vessel, with an accurate reconstruction of its lumen profile. An FD-OCT-based metric that corresponds more closely with physiological significance of lesions may enable more precise guidance of interventional procedures. The aim of this feasibility study was to evaluate a new method for quantifying coronary lesion severity that estimates hyperaemic flow resistance of branched vessel segments imaged by FD-OCT.

METHODS AND RESULTS

An analytical flow model was developed that relates fractional flow reserve (FFR) to the vascular resistance ratio (VRR), a measure of blood flow resistance derived from volumetric FD-OCT lumen profiles. The VRR-FFR relationship was evaluated in 21 patients on whom both pressure measurement and FD-OCT imaging were performed in a random order during maximal hyperaemia. Lesion severity assessed by VRR showed a stronger linear correlation with FFR measurements (before model optimisation [blinded]: r=0.81; p<0.001; root mean square error [RMSE]=0.095 FFR units; after model optimisation [unblinded]: r=0.91; p<0.001; RMSE=0.066 FFR units) than quantitative coronary angiography and FD-OCT-derived measurements of minimum lumen area (r=0.67; p=0.0012) and per cent area stenosis (r=-0.61; p=0.004).

CONCLUSIONS

Accurate volumetric measurement of the lumen profile with FD-OCT correlates more closely with FFR than standard metrics derived from single image cross-sections. VRR shows promise as a method for evaluating lesion severity.

Compliance charts to guide non-complex small artery stenting: validation by quantitative coronary angiography

OBJECTIVE

To determine whether stent sizing derived from manufacturers' compliance charts provides a reasonable in vivo estimate of final minimum lumen diameter (MLD) when compared with quantitative coronary angiography (QCA).

DESIGN

Single-centre measurement comparison study.

SETTING

Tertiary referral university hospital.

PATIENTS

Fifty cases receiving a single stent for non-complex de novo stenosis were randomly selected from the percutaneous coronary intervention database of our high-volume centre. Restenosis, stent thrombosis, bifurcational disease, rotablation, left main or graft stenting, intravascular ultrasound or kissing balloon inflations were exclusion criteria.

MAIN OUTCOME MEASURES

Equality and limits of agreement (LOA) between compliance chart and QCA measurements of final MLD, especially focusing on patients with small stents<3 mm. The paired t test and Bland-Altman plots were used to compare measurements.

RESULTS

There was no significant difference between compliance chart-derived and QCA final MLD (n=50; mean -0.034 mm, SD 0.35, 95% CI -0.132 to +0.064; p=0.49), with reasonable Bland-Altman LOA between the two methods of assessing final MLD in the overall group (LOA -0.72 to +0.66 mm), as well as in the group of particular interest with Derived final MLD <3 mm (n=30; mean 0.019 mm, SD 0.27, 95% CI -0.082 to +0.119; p=0.71; LOA -0.52 to +0.56 mm).

CONCLUSIONS

Compliance charts provide an acceptable estimate of final MLD and are a reasonable guide to sizing during non-complex stenting, especially in small vessels <3 mm.

Optical Coherence Tomography: Potential Clinical Applications

Optical coherence tomography (OCT) is a novel intravascular imaging modality using near-infrared light. By OCT it is possible to obtain high-resolution cross-sectional images of the vascular wall structure and assess the acute and long-term effects of percutaneous coronary intervention. For the time being OCT has been mainly used in research providing new insights into the pathophysiology of the atheromatic plaque and of the vascular response to stenting, however, it seems that there is potential for clinical application of OCT in various fields, such as pre-interventional evaluation of coronary arteries, procedural guidance in coronary interventions, and follow-up assessment of vascular healing after stent implantation. This review will focus on the potential and advantages of OCT in the clinical practice of a catheterization laboratory.

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 mm², 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 mm², 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 mm², 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 studies.

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.

Assessment of coronary stent by optical coherence tomography, methodology and definitions

Optical coherence tomography has emerged as a powerful tool for stent assessment, and in a short time, has become the modality of choice for studying stent and vascular interactions in vivo. In this review, we discuss qualitative and quantitative parameters used for stent assessment by OCT. Various qualitative/quantitative variables of stent assessment are discussed in the perspective of the clinical and research values of each of them.

Utilization of frequency domain optical coherence tomography and fractional flow reserve to assess intermediate coronary artery stenoses: conciliating anatomic and physiologic information

Fractional flow reserve (FFR) and intravascular imaging respectively provide hemodynamic and anatomical assessments of angiographic intermediate stenoses. Frequency domain optical coherence tomography (FD-OCT) is a promising high-resolution imaging modality, but its clinical use in determining severity of coronary disease has yet to be determined. There, we set out to determine the role of FD-OCT to complement FFR in the evaluation of intermediate coronary artery stenoses. FD-OCT was planned in 176 consecutive interventional procedures at our institution to delineate the proper use of FD-OCT in clinical practice. The decision to use other invasive assessments was at the discretion of the operator. This report describes an early series of the 14 patients who underwent FFR of 18 target stenoses in addition to FD-OCT. FD-OCT was successfully performed without complications in all cases. Fractional flow reserve was <0.80 in four patients, with minimal lumen areas and reference vessel diameters ranging from 1.03 to 3.47 mm(2) and 2.60 to 2.94 mm by FD-OCT, respectively. FD-OCT was important to rule out plaque rupture, erosion and thrombosis and to help guide decision to defer PCI in six patients with acute coronary syndrome and FFR > 0.80. FD-OCT was also valuable to guide PCI strategy in tandem lesions with an FFR < 0.80. This initial experience with FD-OCT suggests a potential complementary role of physiological and anatomical assessment to guide decision making in complex clinical scenarios. Future investigations are warranted to validate these findings and define the role of FD-OCT in assessing intermediate lesions.