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.

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.

Efficacy of optical frequency domain imaging in detecting peripheral artery disease: the result of a multi-center, open-label, single-arm study

Optical frequency domain imaging (OFDI) is a high-resolution intracoronary imaging modality with fast automated longitudinal pullback. We aimed to evaluate the ability of performing OFDI from the superficial femoral artery (SFA) to the below-knee (BK) artery. This clinical trial was a multi-center, single-arm, open-label study. The primary endpoint was to obtain a clear image of the intra-vascular lumen from the SFA to the BK artery, specifically  > 270° visualization of the blood vessel lumen with  > 16/21 cross sections. The proportion of the clear image (≥ 85%) was regarded as confirmatory of the ability of OFDI to visualize the vessel lumen. Overall, 20 patients were enrolled. The proportion of the primary endpoint was 90% (18/20), and the pre-specified criterion was successfully attained. The proportion of the clear image assessed by the operator was 100% (20/20), and an additional statistical analysis for the proportion of the visualization,  > 270°, of the blood vessel lumen revealed a significantly higher cut-off value than that for the pre-specified criterion, 85% (p = 0.0315). There were three adverse events not related to OFDI. OFDI achieved acceptable visualization of the vessel lumen without any adverse event related to it. After regulatory approval based on the present study, OFDI will be available as a new option of endovascular imaging for peripheral artery diseases in daily practiceTrial registration: This study was registered in the Japanese Registry of Clinical Trials (jRCT 2052190025, https://jrct.niph.go.jp/latest-detail/jRCT2052190025 ).

Open-Label Multicenter Registry on the Outcomes of In-Stent Restenosis Treated by Balloon Angioplasty with Optical Frequency Domain Imaging in the Superficial Femoral Artery (ISLAND-SFA Study)

Objectives: Balloon angioplasty for in-stent restenosis (ISR) in the superficial femoral artery (SFA) has a high recurrent restenosis rate; however, its mechanism has not been fully and precisely evaluated using high-resolution intravascular imaging. Thus, we aimed to evaluate the relationship between vascular features obtained by optical frequency domain imaging (OFDI) and recurrent restenosis at 6 months. Methods: This was a prospective multicenter single-arm study. OFDI was performed before and after balloon angioplasty, and vascular features were assessed. A multi-layered ISR pattern detected by OFDI was defined as several signal-poor appearances with a high-signal band adjacent to the luminal surface. The primary outcome was defined as recurrent restenosis 6 months after balloon angioplasty. Results: Given that this study was terminated early, only 18 patients completed the 6-month follow-up; of these, 8 developed restenosis. Recurrent restenosis at 6 months tended to be related to a multi-layered ISR pattern (odds ratio (OR), 6.67; 95% confidence interval (CI), 0.81-54.96; p=0.078) and the minimum lumen area (MLA) after balloon angioplasty (OR, 0.71; 95%CI, 0.48-1.04; p=0.077). Conclusion: A multi-layered ISR pattern and MLA after balloon angioplasty detected by OFDI might be risk factors for recurrent ISR in the SFA.

Open-label multicenter registry on the outcomes of peripheral arterial disease treated by balloon angioplasty with optical frequency domain imaging in superficial femoral artery and popliteal artery (OCEAN-SFA study)

Although balloon angioplasty for femoropopliteal artery lesions has been associated with restenosis rates of up to 60% at 12 months, the mechanism of restenosis has not been fully evaluated. The aim of this study was to evaluate the relationship between the vascular features observed on optical frequency domain imaging (OFDI) before and after balloon angioplasty of femoropopliteal artery lesions, and restenosis at 6 months. This study was a prospective multicenter single arm study. OFDI was performed before and after balloon angioplasty and plaque characteristics and vascular features, along with de novo lesions, were assessed. The primary outcome was the presence or absence of restenosis 6 months after balloon angioplasty. Residual platelet reactivity was assessed according to VerifyNow platelet reactivity units (PRUs). The number of patients completing 6 months of follow-up was 47, of which 14 had developed restenosis. Maximum thickness of the dissection flap (odds ratio (OR) 2.71; 95% confidence interval [0.9-8.0]; p = 0.071) and lesion length were identified as risk factors for restenosis (OR 1.015; 95% confidence interval [0.001-0.029]; p = 0.039). The mean PRU at the time of treatment in patients with restenosis was significantly higher than in those without restenosis (286.3 ± 82.6 vs. 208.5 ± 03.6, p = 0.026). Long lesions and major dissection on OFDI after balloon angioplasty for femoropopliteal artery lesions increase restenosis at 6 months. In addition, high residual platelet reactivity at the time of EVT may also be a risk factor for restenosis.Clinical Trial Registration Number UMIN000021120.

Ticagrelor versus clopidogrel in patients undergoing implantation of paclitaxel-eluting stent in the femoropopliteal district: A randomized pilot study using frequency-domain optical coherence tomography

OBJECTIVES

Aim of this study was to evaluate different response in platelet reactivity and vessel healing using high-resolution frequency-domain optical coherence tomography (FD-OCT) in patients with femoropopliteal artery disease treated with ZILVER PTX drug eluting stents (DES), and randomly assigned to clopidogrel or ticagrelor for 12 months.

BACKGROUND

The optimal antithrombotic regimen for long-term management of patients with peripheral artery disease (PAD) after revascularization is poorly defined and often extrapolated from trials performed on patients undergoing percutaneous coronary intervention.

METHODS

In this single center randomized trial 40 patients with femoropopliteal artery disease treated with ZILVER PTX DES stents, were randomized to Ticagrelor (T) + Aspirin for 3 months, subsequently continuing Ticagrelor alone for another 9 months or Clopidogrel (C) + Aspirin for 3 months, subsequently continuing Clopidogrel alone for 9 months. Platelet reactivity via the P2Y12 pathway was evaluated at baseline and at 3 months follow-up, angiographic and FD-OCT follow-up along the entire stented segment was performed at 12 months.

RESULTS

No significant difference between T and C group was found concerning net percentage volume obstruction (29.7% ± 17.6% vs. 31.2% ± 10.7%; p = 0.78). FD-OCT at 12 months showed a high percentage of uncovered stent struts in both groups: 24.2% ± 32.8% in the T group vs 15.3% ± 15.8% in the C group (p = 0.4). Mean values of platelet reactivity units (PRU) at 3 month follow-up were 81 ± 72 in the T group and 200 ± 61 in the C group (p < 0.001).

CONCLUSIONS

Significantly higher platelet reactivity remains in patients treated with clopidogrel as compared to ticagrelor 3 months after PTA and stent implantation. Ticagrelor does not reduce neointimal proliferation in patients treated with DES in the femoropopliteal district as compared with clopidogrel. A large amount of uncovered stent struts at 12-month follow-up was found in these patients regardless of the antiplatelet treatment assumed.

Mechanism of Drug-Eluting Absorbable Metal Scaffold Restenosis

Background:

The pathomechanisms underlying restenosis of the bioabsorbable sirolimus-eluting metallic scaffold (Magmaris) remain unknown. Using serial optical coherence tomography, we investigated causes of restenosis, including the contribution of late scaffold recoil versus neointimal hyperplasia.

Methods:

Patients enrolled in BIOSOLVE-II undergoing serial angiography and optical coherence tomography (post-intervention and follow-up: 6 months and/or 1 year) were analyzed. Patients were divided into 2 groups according to angiographic in-scaffold late lumen loss (LLL) <0.5 or ≥0.5 mm. End points were late absolute scaffold recoil and neointimal hyperplasia area as assessed by optical coherence tomography.

Results:

Serial data were available for analysis from 70 patients (LLL <0.5 mm: n=41; LLL ≥0.5 mm: n=29). Patient and lesion characteristics were comparable, and there was no significant difference in mean and minimal scaffold area between groups at post-intervention. Late absolute scaffold recoil was less among patients with LLL <0.5 mm (0.53±0.68 mm 2 ) compared with those with LLL ≥0.5 mm (1.48±1.20 mm 2 ; P <0.001). Neointimal hyperplasia area was smaller among patients with LLL <0.5 mm at follow-up (1.47±0.33 mm 2 ) compared with patients with LLL ≥0.5 mm (1.68±0.34 mm 2 ; P =0.013). In a matched-frame analysis (post-intervention and follow-up), late absolute scaffold recoil varied according to the underlying plaque type (lipid: 0.63±1.23 mm 2 ; calcified: 0.81±1.44 mm 2 ; and fibrous: 1.20±1.52 mm 2 ; P <0.001), while there was no difference with regards to neointimal hyperplasia area ( P =0.132).

Conclusions:

In addition to neointimal hyperplasia, late scaffold recoil contributed significantly to LLL of sirolimus-eluting absorbable metal scaffolds. The extent of late scaffold recoil was dependent on the underlying plaque morphology and was the highest among fibrotic lesions.

Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01960504.

A post-market, multi-vessel evaluation of the imaging of peripheral arteries for diagnostic purposeS comparing optical Coherence tomogrApy and iNtravascular ultrasound imaging (SCAN)

Background

Intravascular imaging plays an important part in diagnosis of vascular conditions and providing insight for treatment strategy. Two main imaging modalities are intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The objective of this study was to prove non-inferiority of OCT imaging to IVUS images in matched segments of peripheral vessels in patients with suspected peripheral vascular disease.

Methods

The SCAN study was a prospective, non-inferiority clinical study of matched IVUS and OCT images collected along defined segments of peripheral vessels from twelve subjects (mean age 68 ± 10.3 years; 10 men) displaying symptoms of vascular disease. Luminal diameters were measured by both imaging systems at the distal, middle, and proximal points of the defined segments. Three blinded interventional radiologists evaluated the quality of both imaging modalities in identifying layered structures (3-point grading), plaque (5-point grading), calcification (5-point grading), stent structure (3-point grading), and artifacts (3-point grading) from 240 randomly ordered images. Mean grading scores and luminal diameters were calculated and analyzed with Student’s t-Test and Mann-Whitney-Wilcoxon testing. Intrareader reproducibility was calculated by intraclass correlation (ICC) analysis.

Results

The mean scoring of plaque, calcification, and vascular stent struts by the three readers was significant better in terms of image quality for OCT than IVUS (p < 0.001, p = 0.001, p = 0.004, respectively). The mean scores of vessel wall component visibility and artifacts generated by the two imaging systems were not significantly different (p = 0.19, p = 0.07, respectively). Mean vessel luminal diameter and area at three specific locations within the vessels were not significantly different between the two imaging modalities. No patient injury, adverse effect or device malfunction were noted during the study.

Conclusions

Imaging by OCT provides the physician with better visualization of some vessel and plaque chacteristics, but both IVUS and OCT imaging are safe and effective methods of examining peripheral vessels in order to perform diagnostic assessment of peripheral vessels and provide information necessary for the treatment strategy of peripheral artery disease.

Trial registration

NCT03480685 registered on 29 March 2018.

Bioresorbable scaffold implantation in STEMI patients: 5 years imaging subanalysis of PRAGUE-19 study

Background

Bioresorbable scaffold (BRS) Absorb™ clinical use has been stopped due to higher rate of device thrombosis. Scaffold struts persist longer than 2 years in the vessel wall. Second generation devices are being developed. This study evaluates long-term invasive imaging in STEMI patients.

Methods

PRAGUE-19 study is an academic study enrolling consecutive STEMI patients with intention to implant Absorb™ BRS. A total of 83 STEMI patients between December 2012 and March 2014 fulfilled entry criteria. Coronary angiography and optical coherence tomography at 5 year follow-up was performed in 25 patients.

Results

Primary combined clinical endpoint (death, myocardial infarction or target vessel revascularization) occurred in 12.6% during the five-year follow-up with overall mortality 6.3%. Definite scaffold thrombosis occurred in 2 patients in the early phase after BRS implantation. Quantitative coronary angiography after 5 years demonstrated low late lumen loss of 0.11 ± 0.35 mm with binary restenosis rate of 0%. Optical coherence tomography demonstrated complete resorption of scaffold struts and mean lumen diameter of 3.25 ± 0.30 and 3.22 ± 0.49 (P = 0.73) at baseline and after 5 years, respectively. Three patients developed small coronary artery aneurysm in the treated segment.

Conclusion

Invasive imaging results 5 years after BRS implantation in STEMI showed complete resorption of scaffold struts and stable lumen vessel diameter.

Trial registration ISRCTN43696201 (retrospectivelly registred, June 7th, 2019). https://www.isrctn.com/ISRCTN43696201.

Associations of coronary plaque characteristics by integrated backscatter intravascular ultrasound with detectability of vessel external elastic lamina using optical frequency domain imaging in human coronary arteries: A sub-analysis of the MISTIC-1 trial

OBJECTIVES

We sought to examine associations between plaque characteristics by intravascular ultrasound (IVUS) and detectability of external elastic lamina (EEL) by optical frequency domain imaging (OFDI) in human coronary arteries.

BACKGROUND

It is often challenging to detect EEL which represents vessel size by light-based imaging modalities due to light intensity attenuation through atherosclerotic plaque.

METHODS

IVUS and OFDI prior to stent implantation were sequentially investigated per protocol. We identified corresponding cross-sections by minimum lumen area (MLA) or just distally to side branches as anatomical landmarks. Plaque characterization was determined by integrated backscatter IVUS analysis. We categorized detectable EEL arc by OFDI into four groups: 0≤ and <1 quadrant (group 1), 1≤ and <2 quadrants (group 2), 2≤ and <3 quadrants (group 3), or 3≤ and <4 quadrants (group 4).

RESULTS

We prospectively studied 103 vessels in 93 patients with stable coronary artery disease. Corresponding 711 cross-sections were analyzed. Cross-sections with detectable EEL arc <2 quadrants (group 1 or 2) were observed in 86.1% of MLA sites but only in 29.3% of non-MLA sites (p < .05). Percentage plaque area (%PA) appeared to be the strongest predictor to detect EEL arc <2 quadrants with the cut-off of 60.3% (AUC 0.90; sensitivity 79.8%, specificity 85.5%). Lipid pool and calcification remained statistically significant in predicting detectable EEL arc <2 quadrants after adjustment with %PA.

CONCLUSIONS

Presence of large plaque burden, lipid pool, and calcification significantly predicts the detectability of EEL by OFDI assessment. Locations with detectable EEL arc <2 quadrants should thus be avoided for optimal stent landing zone.

Long-term follow-up after bioresorbable vascular scaffold implantation in STEMI patients: PRAGUE-19 study update

AIMS

Early clinical results after implantation of bioresorbable vascular scaffolds (BVS) in ST-elevation myocardial infarction (STEMI) are encouraging, but long-term data are missing. This study evaluates long-term outcome in STEMI patients with implanted BVS.

METHODS AND RESULTS

The PRAGUE-19 study is an academic study enrolling consecutive STEMI patients with the intention to implant BVS. A total of 580 STEMI patients were screened between December 2012 and March 2015; 117 patients fulfilled entry criteria and BVS was successfully implanted in 114 (97%) of them. The primary combined clinical endpoint (death, reinfarction or target vessel revascularisation) occurred in 11.5% during the mean follow-up period of 730±275 days with overall mortality of 4.4%. Definite scaffold thrombosis occurred in two patients in the early phase after BVS implantation; there was no late thrombosis. Quantitative coronary angiography (10 patients) at three years demonstrated late lumen loss of 0.2±0.33 mm and optical coherence tomography showed minimal lumen area of 5.3±1.37 mm2 and neointimal hyperplasia area of 2.9±0.48 mm2. BVS struts were still visible at three years and 99.4% of them were well apposed and covered.

CONCLUSIONS

Encouraging clinical and imaging results after BVS implantation in STEMI patients persist during long-term follow-up.

Impact of analysis interval size on the quality of optical frequency domain imaging assessments of stent implantation for lesions of the superficial femoral artery

OBJECTIVES

This study aimed to investigate the influence of analysis interval size on optical frequency domain imaging (OFDI) assessment of stent therapy for lesions of the superficial femoral artery (SFA).

BACKGROUND

No consensus or validating data are available with respect to the methodology of intravascular imaging analysis for the peripheral arteries.

METHODS

OFDI was performed for 30 SFA lesions, during endovascular therapy and at the 6-month follow-up. Initially, lumen and stent borders were traced at 1-mm axial intervals. Volumes were calculated using a PC-based software, and the volume index (VI) was defined as the volume divided by the stent length. Two additional OFDI analyses were performed using 2-mm and 5-mm intervals, thereby reducing the number of cross-sectional image frames analyzed.

RESULTS

The mean stent length was 89.7 ± 35.2 mm. The mean difference in baseline minimum lumen area (MLA) was 0.4 mm² between MLA values from the 1-mm and 2-mm interval analyses, and 2.2 mm² between MLA values from the 1-mm and 5-mm interval analyses. In volumetric analysis, there were excellent correlations and good agreements for stent, lumen, and neointimal VI measurements obtained on the basis of different analysis intervals.

CONCLUSIONS

Using large intervals in OFDI analyses of SFA lesions resulted in few differences in measurement variability of volumetric parameters. However, planar analysis for MLA assessment can be susceptible to high variability when large intervals are applied. © 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.

Intra- and interobserver reliability and intra-catheter reproducibility using frequency domain optical coherence tomography for the evaluation of morphometric stent parameters and qualitative assessment of stent strut coverage

PURPOSE

Frequency-domain optical coherence tomography (FD-OCT) is a high-resolution imaging tool (~10-15 μm), which enables near-histological in-vivo images of the coronary vessel wall. The use of the technique is increasing, both for research- and clinical purposes. This study sought to investigate the intra- and interobserver reliability, as well as the intra-catheter reproducibility of quantitative FD-OCT-assessment of morphometric stent parameters and qualitative FD-OCT-evaluation of strut coverage in 10 randomly selected 6-month follow-up Nobori® biolimus-eluting stents (N-BESs).

METHODS

Ten N-BESs (213 cross sectional areas (CSAs) and 1897 struts) imaged with OCT 6 months post-implantation were randomly selected and analyzed by 2 experienced analysts, and the same 10 N-BESs were analyzed by one of the analysts 3 months later. Further, 2 consecutive pullbacks randomly performed in another 10 N-BESs (219 CSAs and 1860 struts) were independently assessed by one of the analysts.

RESULTS

The intraobserver variability with regard to relative difference of mean luminal area and mean stent area at the CSA-level was very low: 0.1%±1.4% and 0.5%±3.2%. Interobserver variability also proved to be low: -2.1%±3.3% and 2.1%±4.6%, and moreover, very restricted intra-catheter variation was observed: 0.02%±6.8% and -0.18%±5.2%. The intraobserver-, interobserver- and intra-catheter reliability for the qualitative evaluation of strut coverage was found to be: kappa (κ)=0.91 (95% confidence interval (CI): 0.88-0.93, p<0.01), κ=0.88 (95% CI: 0.85-0.91, p<0.01), and κ=0.73 (95% CI: 0.68-0.78, p<0.01), respectively.

CONCLUSIONS

FD-OCT is a reproducible and reliable imaging tool for quantitative evaluation of stented coronary segments, and for qualitative assessment of strut coverage.

Evaluation of the influence of cardiac motion on the accuracy and reproducibility of longitudinal measurements and the corresponding image quality in optical frequency domain imaging: an ex vivo investigation of the optimal pullback speed

Longitudinal measurement using intravascular ultrasound is limited because the motorized pullback device assumes no cardiac motion. A newly developed intracoronary imaging modality, optical frequency domain imaging (OFDI), has higher resolution and an increased auto-pullback speed with presumably lesser susceptibility to cardiac motion artifacts during pullback for longitudinal measurement; however, it has not been fully investigated. We aimed to clarify the influence of cardiac motion on the accuracy and reproducibility of longitudinal measurements obtained using OFDI and to determine the optimal pullback speed. This ex vivo study included 31 stents deployed in the mid left anterior descending artery under phantom heartbeat and coronary flow simulation. Longitudinal stent lengths were measured twice using OFDI at three pullback speeds. Differences in stent lengths between OFDI and microscopy and between two repetitive pullbacks were assessed to determine accuracy and reproducibility. Furthermore, three-dimensional (3D) reconstruction was used for evaluating image quality. With regard to differences in stent length between OFDI and microscopy, the intraclass correlation coefficient values were 0.985, 0.994, and 0.995 at 10, 20, and 40 mm/s, respectively. With regard to reproducibility, the values were 0.995, 0.996, and 0.996 at 10, 20, and 40 mm/s, respectively. 3D reconstruction showed a superior image quality at 10 and 20 mm/s compared with that at 40 mm/s. OFDI demonstrated high accuracy and reproducibility for longitudinal stent measurements. Moreover, its accuracy and reproducibility were remarkable at a higher pullback speed. A 20-mm/s pullback speed may be optimal for clinical and research purposes.

Measurement of the blood flow rate and velocity in coronary artery stenosis using intracoronary frequency domain optical coherence tomography: Validation against fractional flow reserve

OBJECTIVES

The main objective of this study was to assess the blood flow rate and velocity in coronary artery stenosis using intracoronary frequency domain optical coherence tomography (FD-OCT). A correlation between fractional flow reserve (FFR) and FD-OCT derived blood flow velocity is also included in this study.

METHODS & RESULTS

A total of 20 coronary stenoses in 15 patients were assessed consecutively by quantitative coronary angiography (QCA), FFR and FD-OCT. A percutaneous coronary intervention (PCI) optimization system was used in this study which combines wireless FFR measurement and FD-OCT imaging in one platform. Stenoses were labelled severe if FFR ≤ 0.8. Blood flow rate and velocity in each stenosis segment were derived from the volumetric analysis of the FD-OCT pull back images. The FFR value was ≤ 0.80 in 5 stenoses (25%). The mean blood flow rate in severe coronary stenosis (n = 5) was 2.54 ± 0.55 ml/s as compared to 4.81 ± 1.95 ml/s in stenosis with FFR > 0.8 (n = 15). A good and significant correlation between FFR and FD-OCT blood flow velocity in coronary artery stenosis (r = 0.74, p < 0.001) was found.

CONCLUSION

The assessment of stenosis severity using FD-OCT derived blood flow rate and velocity has the ability to overcome many limitations of QCA and intravascular ultrasound (IVUS).

Optical coherence tomography-based predictors for creatine kinase-myocardial band elevation after elective percutaneous coronary intervention for in-stent restenosis

OBJECTIVES

We evaluated whether morphological characteristics of neointimal tissue of in-stent restenosis (ISR) lesions assessed by optical coherence tomography (OCT) affect periprocedural elevation of creatine kinase-myocardial band (CK-MB).

BACKGROUND

The impact of neointimal characteristics of ISR lesions on periprocedural myocardial injury has not been sufficiently investigated.

METHODS

A total of 125 patients with ISR lesions underwent elective percutaneous coronary intervention (PCI) and pre-PCI OCT examination. Measurements of CK-MB were performed upon hospitalization, before PCI, and every 8 hr for 24 hr after PCI. CK-MB elevation was defined as levels above the 99th percentile of the upper reference limit. Neoatherosclerosis was defined as neointima with lipid or calcification.

RESULTS

Post-PCI CK-MB elevation was observed in 20 (16.0%) patients. The maximum length of consecutive cross-sections with neoatherosclerosis on the longitudinal axis of the stent was significantly larger in patients with post-PCI CK-MB elevation than in those without [8.8 mm (1.5-10.4) vs. 0.0 mm (0.0-1.0), P < 0.001], and thin-cap fibroatheroma (TCFA) were more frequently observed at the site of minimal lumen cross-sectional area in patients with post-PCI CK-MB elevation (55.0% vs. 1.9%, P < 0.001). Multivariate analysis revealed that the maximum length of segments with neoatherosclerosis [odds ratio (OR), 1.463; 95% confidence interval (CI), 1.090-1.962; P = 0.011] and TCFA (OR, 14.328; 95% CI, 1.118-183.628; P = 0.041) were independent predictors for post-PCI CK-MB elevation.

CONCLUSIONS

A greater axial length of neoatherosclerosis and the presence of TCFA at the most stenotic site were significantly associated with post-PCI CK-MB elevation in ISR lesions.

Quantitative angiography and optical coherence tomography for the functional assessment of nonobstructive coronary stenoses: comparison with fractional flow reserve

BACKGROUND

The purpose was to compare 3-dimensional quantitative coronary angiography (3D-QCA) with optical coherence tomography (OCT) for the functional assessment of nonobstructive coronary stenoses, as evaluated by fractional flow reserve (FFR).

METHODS

Fifty-five nonobstructive coronary stenoses (30%-50% diameter stenosis by visual estimation) were assessed in 36 patients using FFR, 2-dimensional QCA (2D-QCA), 3D-QCA, and OCT.

RESULTS

Angiographic stenosis severity by 2D-QCA was 34% ± 13% diameter stenosis, and minimal lumen diameter (MLD) was 1.77 ± 0.58 mm. Fractional flow reserve values were 0.85 ± 0.10. Correlation coefficients between FFR and MLD or minimal lumen area (MLA) were highly significant for both 2D- and 3D-QCA (all P < .001), but higher R(2) values were observed for 3D-QCA measurements. Although significant, correlation coefficients between OCT and FFR data were weak (R(2) = 0.28, P = .001 for MLD and R(2) = 0.23, P = .003 for MLA). Correlation coefficients with FFR were significantly higher for 3D-QCA than for OCT (P values for MLD and MLA = .043 and .042, respectively). Nonobstructive stenoses with MLD >1.53 mm or MLA >2.43 mm(2) are unlikely to be hemodynamically significant.

CONCLUSIONS

In nonobstructive coronary stenoses, anatomical parameters derived from 3D-QCA can best identify lesions with preserved FFR values.

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.

Reproducibility of qualitative assessment of stent struts coverage by optical coherence tomography

Assessment of stent strut coverage by optical coherence tomography (OCT) is not standardized. The methodology most commonly used is based on a visual binary qualitative assessment (strut covered or not). However, the influence of magnification (zoom setting) to the inter- and intra-observer agreements has not yet been evaluated. Aim of our study was therefore to evaluate the agreements of this approach, taking into account various zoom settings. 126 struts from 10 selected frames were independently evaluated by four observers using a stepwise approach increasing the zoom setting as following: (1) full view of the lumen (FV), (2) half view of the lumen (HV) and (3) a quarter view of the lumen (QV). Intra- and inter-observer agreements (κ) were assessed. The rate of uncoverage was determined for each strut as the number of times it was defined as uncovered divided by the total number of observations (maximum 12 = 3 zoom settings × 4 analysts) and expressed as percentage. The inter-observer κ values (mean [range]) were 0.32 [0.07-0.63], 0.40 [0.18-0.69] and 0.33 [0.09-0.6], within FV, HV and QV respectively. The intra-observer κ values were 0.60 [0.50-0.70], 0.75 [0.75-0.76] and 0.60 [0.50-0.70], within FV, HV and QV respectively. By increasing zoom setting the κ value of intra-observer agreement was 0.74 [0.58-0.83] (from FV to HV), 0.70 [0.56-0.83] (from HV to QV) and 0.70 [0.37-0.86] (from FV to QV). Overall, the rate of uncoverage was 15.5% [8.3-100%]. The OCT qualitative evaluation of strut coverage has wide inter and intra-observer agreements and is dependent of the zoom setting used during the analysis. A more reproducible approach would be needed to eventually increase the probability to link uncovered struts with clinical events.

Reproducibility of coronary optical coherence tomography for lumen and length measurements in humans (The CLI-VAR [Centro per la Lotta contro l'Infarto-VARiability] study)

Frequency-domain optical coherence tomography (FD-OCT) is becoming a useful diagnostic tool for coronary imaging for quantitative coronary analysis. Second-generation FD-OCT produces detailed coronary lumen images. However, the reproducibility of coronary measurements using FD-OCT in humans has not been thoroughly explored. Our goal was to determine the intraobserver, interobserver, and interpullback reproducibility of the in vivo FD-OCT measurements of the lumen area and/or lesion length. Twenty-five patients undergoing coronary angioplasty were included. In all subjects, FD-OCT pullbacks (20 mm/s) were acquired twice from the same coronary segment different from the target lesion, at an interval of 5 minutes, with no other intervention. A total of 9,396 cross-sectional lumen area frames and the relative coronary lesion length of each pullback were analyzed off-line with dedicated software by 2 independent expert readers (A and B). We compared the lumen area and length measurements as follows: pullback 1, read by reader A twice at an interval of 7 days (intraobserver analysis); pullback 1, independently read by readers A and B (interobserver comparison); and pullback 1 versus pullback 2, read by reader A (interpullback comparison). The per-segment and per-frame analyses showed very high and significant correlation coefficients for the interobserver, intraobserver, and interpullback comparisons for the lumen area and lesion length (R ≥0.95 and p <0.001 in all cases). Accordingly, the Bland-Altman estimates of bias showed nonsignificant differences in the interobserver, intraobserver, and interpullback comparisons at all levels, with average biases never >0.150 mm(2) for the lumen area or 0.200 mm for the lesion length. In conclusion, coronary imaging using FD-OCT showed excellent reproducibility, with low intraobserver, interobserver, and interpullback variability for both lumen area and lesion length measurements in humans. Thus, FD-OCT can be proposed for precise analysis in the catheterization laboratory to guide decision making and in clinical trials focusing on imaging end points.

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.

Optical coherence tomography: from physical principles to clinical applications

Optical coherence tomography is a new endocoronary imaging modality employing near infrared light, with very high axial resolution. We will review the physical principles, including the old time domain and newer Fourier domain generations, clinical applications, controversies and perspectives of optical coherence tomography.

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.

Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies: a report from the International Working Group for Intravascular Optical Coherence Tomography Standardization and Validation

OBJECTIVES

The purpose of this document is to make the output of the International Working Group for Intravascular Optical Coherence Tomography (IWG-IVOCT) Standardization and Validation available to medical and scientific communities, through a peer-reviewed publication, in the interest of improving the diagnosis and treatment of patients with atherosclerosis, including coronary artery disease.

BACKGROUND

Intravascular optical coherence tomography (IVOCT) is a catheter-based modality that acquires images at a resolution of ~10 μm, enabling visualization of blood vessel wall microstructure in vivo at an unprecedented level of detail. IVOCT devices are now commercially available worldwide, there is an active user base, and the interest in using this technology is growing. Incorporation of IVOCT in research and daily clinical practice can be facilitated by the development of uniform terminology and consensus-based standards on use of the technology, interpretation of the images, and reporting of IVOCT results.

METHODS

The IWG-IVOCT, comprising more than 260 academic and industry members from Asia, Europe, and the United States, formed in 2008 and convened on the topic of IVOCT standardization through a series of 9 national and international meetings.

RESULTS

Knowledge and recommendations from this group on key areas within the IVOCT field were assembled to generate this consensus document, authored by the Writing Committee, composed of academicians who have participated in meetings and/or writing of the text.

CONCLUSIONS

This document may be broadly used as a standard reference regarding the current state of the IVOCT imaging modality, intended for researchers and clinicians who use IVOCT and analyze IVOCT data.

Morphometric assessment of coronary stenosis relevance with optical coherence tomography: a comparison with fractional flow reserve and intravascular ultrasound

OBJECTIVES

The study sought to assess the diagnostic efficiency of optical coherence tomography (OCT) in identifying hemodynamically severe coronary stenoses as determined by fractional flow reserve (FFR). Concomitant OCT and intravascular ultrasound (IVUS) area measurements were performed in a subgroup of patients to compare the diagnostic efficiency of both techniques.

BACKGROUND

The value of OCT to determine stenosis severity remains unsettled.

METHODS

Sixty-one stenoses with intermediate angiographic severity were studied in 56 patients. Stenoses were labeled as severe if FFR ≤0.80. OCT interrogation was performed in all cases, with concomitant IVUS imaging in 47 cases.

RESULTS

Angiographic stenosis severity was 50.9 ± 8% diameter stenosis with 1.28 ± 0.3 mm minimal lumen diameter. FFR was ≤0.80 in 28 (45.9%) stenoses. An overall moderate diagnostic efficiency of OCT was found (area under the curve [AUC]: 0.74; 95% confidence interval [CI]: 0.61 to 0.84), with sensitivity/specificity of 82%/63% associated with an optimal cutoff value of 1.95 mm(2). Comparison of the results in patients with simultaneous IVUS and OCT imaging revealed no significant differences in the diagnostic efficiency of OCT (AUC: 0.70; 95% CI: 0.55 to 0.83) and IVUS (AUC. 0.63; 95% CI: 0.47 to 0.77; p = 0.19). Sensitivity/specificity for IVUS was 67%/65% for an optimal cutoff value of 2.36 mm(2). In the subgroup of small vessels (reference diameter <3 mm) OCT showed a significantly better diagnostic efficiency (AUC: 0.77; 95% CI: 0.60 to 0.89) than IVUS (AUC: 0.63; 95% CI: 0.46 to 0.78) to identify functionally significant stenoses (p = 0.04).

CONCLUSIONS

OCT has a moderate diagnostic efficiency in identifying hemodynamically severe coronary stenoses. Although OCT seems slightly superior to IVUS for this purpose (particularly in vessels <3 mm), its low specificity precludes its use as a substitute of FFR for functional stenosis assessment.

Automatic vessel lumen segmentation and stent strut detection in intravascular optical coherence tomography

PURPOSE

Optical coherence tomography (OCT) is a catheter-based imaging method that employs near-infrared light to produce high-resolution cross-sectional intravascular images. The authors propose a segmentation technique for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH).

METHODS

A clinical dataset of frequency-domain OCT scans of the human femoral artery was analyzed. First, a segmentation method based on the Markov random field (MRF) model was employed for lumen area identification. Second, textural and edge information derived from local intensity distribution and continuous wavelet transform (CWT) analysis were integrated to extract the inner luminal contour. Finally, the stent strut positions were detected via the introduction of each strut wavelet response across scales into a feature extraction and classification scheme in order to optimize the strut position detection.

RESULTS

The inner lumen contour and the position of stent strut were extracted with very high accuracy. Compared with manual segmentation by an expert vascular physician the automatic segmentation had an average overlap value of 0.937 ± 0.045 for all OCT images included in the study. The strut detection accuracy had an area under the curve (AUC) value of 0.95, together with sensitivity and specificity average values of 0.91 and 0.96, respectively.

CONCLUSIONS

A robust automatic segmentation technique integrating textural and edge information for vessel lumen border extraction and strut detection in intravascular OCT images was designed and presented. The proposed algorithm may be employed for automated quantitative morphological analysis of in-stent neointimal hyperplasia.

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.

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.

Invasive imaging technologies: can we reconcile light and sound?

Since the introduction of intravascular, catheter-based invasive imaging and diagnostic tools in the catheterization laboratories two decades ago, the functional assessment of angiographically moderate or ambiguous lesions by fractional flow reserve measurements represents the established standard of care today. Likewise, intravascular ultrasound (IVUS) is widely accepted to guide treatment strategy in complex lesions, such as long or left main stem lesions. Developments are driven by the clinical interest to optimize treatment, prevent periprocedural complications, understand treatment failure and understand progression of atherosclerosis. As a result, a variety of devices are now clinically available that enable detection and monitoring of specific plaque features over time, such as the presence of necrotic core by IVUS-VH, a lipid-core plaque by near infrared (NIR) spectroscopy or a thin fibrous cap atheroma by optical coherence tomography (OCT). As the physical boundaries for both light and sound are different, these imaging technologies offer different advantages and limitations. Light-based technologies offer unparalleled high image resolution (OCT) or unparalleled high sensitivity and specificity for distinct plaque components (NIR spectroscopy), whereas conventional IVUS offers a much better tissue penetration. From a clinical perspective, both types of information are valuable. Ideally, this information should easily and in real time be available in the catheterization laboratory, consisting of co-registered datasets gained during a single catheter pullback. On this background, a combined NIR spectroscopy and IVUS catheter has recently been introduced for clinical use. The article discusses the potential and limitations of these different technologies. They may allow advanced coronary plaque diagnosis in a fast, accurate, reliable, user- and patient-friendly manner and, as such, can help to improve clinical practice today and therapeutic options in the future.

Evaluation with in vivo optical coherence tomography and histology of the vascular effects of the everolimus-eluting bioresorbable vascular scaffold at two years following implantation in a healthy porcine coronary artery model: implications of pilot results for future pre-clinical studies

To quantify with in vivo OCT and histology, the device/vessel interaction after implantation of the bioresorbable vascular scaffold (BVS). We evaluated the area and thickness of the strut voids previously occupied by the polymeric struts, and the neointimal hyperplasia (NIH) area covering the endoluminal surface of the strut voids (NIH_EV), as well as the NIH area occupying the space between the strut voids (NIH_BV), in healthy porcine coronary arteries at 2, 3 and 4 years after implantation of the device. Twenty-two polymeric BVS were implanted in the coronary arteries of 11 healthy Yucatan minipigs that underwent OCT at 2, 3 and 4 years after implantation, immediately followed by euthanasia. The areas and thicknesses of 60 corresponding strut voids previously occupied by the polymeric struts and the size of 60 corresponding NIH_EV and 49 NIH_BV were evaluated with both OCT and histology by 2 independent observers, using a single quantitative analysis software for both techniques. At 3 and 4 years after implantation, the strut voids were no longer detectable by OCT or histology due to complete polymer resorption. However, analysis performed at 2 years still provided clear delineation of these structures, by both techniques. The median [ranges] areas of these strut voids were 0.04 [0.03–0.16] and 0.02 [0.01–0.07] mm² by histology and OCT, respectively. The mean (±SD) thickness by histology and OCT was 220 ± 40 and 120 ± 20 μm, respectively. The median [ranges] NIH_EV by histology and OCT was 0.07 [0.04–0.20] and 0.03 [0.01–0.08] mm², while the mean (±SD) NIH_BV by histology and OCT was 0.13 ± 0.07 and 0.10 ± 0.06 mm². Our study indicates that in vivo OCT of the BVS provides correlated measurements of the same order of magnitude as histomorphometry, and is reproducible for the evaluation of certain vascular and device-related characteristics. However, histology systematically gives larger values for all the measured structures compared to OCT, at 2 years post implantation.

Quantitative multi-modality imaging analysis of a fully bioresorbable stent: a head-to-head comparison between QCA, IVUS and OCT

The bioresorbable vascular stent (BVS) is totally translucent and radiolucent, leading to challenges when using conventional invasive imaging modalities. Agreement between quantitative coronary angiography (QCA), intravascular ultrasound (IVUS) and optical coherence tomography (OCT) in the BVS is unknown. Forty five patients enrolled in the ABSORB cohort B1 study underwent coronary angiography, IVUS and OCT immediately post BVS implantation, and at 6 months. OCT estimated stent length accurately compared to nominal length (95% CI of the difference: -0.19; 0.37 and -0.15; 0.47 mm(2) for baseline and 6 months, respectively), whereas QCA incurred consistent underestimation of the same magnitude at both time points (Pearson correlation = 0.806). IVUS yielded low accuracy (95% CI of the difference: 0.77; 3.74 and -1.15; 3.27 mm(2) for baseline and 6 months, respectively), with several outliers and random variability test-retest. Minimal lumen area (MLA) decreased substantially between baseline and 6 months on QCA and OCT and only minimally on IVUS (95% CI: 0.11; 0.42). Agreement between the different imaging modalities is poor: worst agreement Videodensitometry-IVUS post-implantation (ICCa 0.289); best agreement IVUS-OCT at baseline (ICCa 0.767). All pairs deviated significantly from linearity (P < 0.01). Passing-Bablok non-parametric orthogonal regression showed constant and proportional bias between IVUS and OCT. OCT is the most accurate technique for measuring stent length, whilst QCA incurs systematic underestimation (foreshortening) and solid state IVUS incurs random error. Volumetric calculations using solid state IVUS are therefore not reliable. There is poor agreement for MLA estimation between all the imaging modalities studied, including IVUS-OCT, hence their values are not interchangeable.