Frequency-domain Optical Coherence Tomography Imaging Research Articles

Assessing the efficacy of saline flush in frequency-domain optical coherence tomography for intracoronary imaging

BackgroundThe increased amount of contrast media in frequency-domain optical coherence tomography (FD-OCT) imaging during percutaneous coronary intervention (PCI) has raised potential concerns regarding impairment of renal function.ObjectivesThis study aimed to evaluate the effectiveness of heparinized saline flush in FD-OCT-guided PCI and identify clinical factors contributing to optimal image quality.MethodsWe retrospectively collected 100 lesions from 90 consecutive patients, and a total of 200 pullbacks were analyzed for the initial and final evaluation in which saline was used as the flushing medium.ResultsThe study population had a mean age of 73, with 52% having chronic kidney disease (CKD). The median amount of contrast used was 28 ml, and no complications were observed associated with saline flush OCT. Imaging quality was then categorized as excellent, good, or unacceptable. Among the total runs, 87% demonstrated clinically acceptable image quality, with 66.5% classified as excellent images and 20.5% classified as good images. Independent predictors of excellent images included lumen area stenosis ≥ 70% (adjusted odds ratio [OR] 2.37, 95% confidence interval [CI] 1.02–5.47, P = 0.044), and the use of intensive flushing (adjusted OR 2.06, 95% CI 1.11–3.86, P = 0.023) defined as a deep engagement of guiding catheter (GC) or a selective insertion of guide extension catheter (GE). Intensive flushing was performed in 60% of the total pullbacks, and it was particularly effective in improving image quality in the left coronary artery (LCA).ConclusionThe use of saline flush during FD-OCT imaging was safe and feasible, which had a benefit in renal protection with adequate imaging quality.

TCTAP A-059 Comparison of Contrast Media Versus Hydroxyethyl Starch for Frequency-Domain Optical Coherence Tomography Imaging in Coronary Artery Disease

TCTAP A-059 Comparison of Contrast Media Versus Hydroxyethyl Starch for Frequency-Domain Optical Coherence Tomography Imaging in Coronary Artery Disease

Plaque microstructures during metformin therapy in type 2 diabetic subjects with coronary artery disease: optical coherence tomography analysis.

While metformin is recommended as a first-line cardioprotective therapy for type 2 diabetic patients, whether it exerts direct effects on atherosclerotic plaque remains uncertain. The current study characterized coronary plaque microstructures in type 2 diabetic patients who received metformin. We retrospectively analyzed 409 non-culprit lipid plaques in 313 type 2 diabetic patients with coronary artery disease (CAD) by using frequency-domain optical coherence tomography (FD-OCT) imaging. FD-OCT derived plaque microstructures were compared in patients stratified according to metformin use. A proportion of 38.6% of study subjects received metformin. Patients receiving metformin more likely exhibited a history of hypertension (79.3% vs. 67.1%, P=0.03) and metabolic syndrome (52.8% vs. 36.4%, P=0.01). On FD-OCT imaging, the prevalence of lipid plaque was lower in the metformin group (66.2% vs. 77.9%, P=0.03). Furthermore, the metformin group demonstrated plaques with a smaller lipid arc (median: 168.7° vs. 208.5°, P=0.008), shorter longitudinal length (media: 5.1 vs. 9.1 mm, P=0.04), and a lower frequency of cholesterol crystal (3.9% vs. 18.2%, P=0.01) and spotty calcification (3.9% vs. 34.8%, P=0.008). These differences remained significant after adjusting for clinical characteristics and glycemic control. However, in patients who received insulin, the favourable effect of metformin on lipid arc was not observed (insulin user: P=0.87; insulin non-user: P=0.009; P value for interaction between two groups, P=0.02). Metformin use was associated with a lower prevalence of vulnerable plaque features in type 2 diabetic patients with CAD, especially insulin non-user. These findings suggest the potential of metformin to exert direct plaque stabilization effects in type 2 diabetic subjects.

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.

Head-to-head comparison of quantitative measurements between intravascular imaging systems: An in vitro phantom study

IntroductionThe present study aimed to compare the accuracy of quantitative measurements by contemporary intravascular imaging systems including optical frequency domain imaging (OFDI), frequency domain optical coherence tomography (FD-OCT), and 6 intravascular ultrasound (IVUS) systems.MethodsWe imaged five cylindrical phantom models made from an acrylic resin with known lumen diameters (1.51, 2.03, 3.04, 4.04, and 5.04 mm, respectively) using OFDI (FastView and LUNAWAVE, Terumo), FD-OCT (Dragonfly JP and ILUMIEN OPTIS, Abbott Vascular), and 6 mechanically rotating IVUS systems including a system, two 40-MHz, one 45-MHz, two 60-Mhz and one broad-band frequency IVUS systems. The OFDI, FD-OCT, and IVUS images were obtained using automated motorized pullback in a tank filled with 37-degree Celsius saline and, in cases of OFDI and FD-OCT, contrast-saline mixture (1:1 ratio) and contrast under the system setting of the refractive index for the corresponding flush medium.ResultsAll the imaging systems showed good accuracy and excellent precision of lumen measurement with the relative differences between the measured diameter and actual phantom diameter being ranging from −2.9% to 8.0% and minimum standard deviations of the measured diameters (≤0.02 mm).ConclusionThe present study demonstrated that contemporary intravascular imaging systems including OFDI, FD-OCT, and IVUS provided clinically acceptable accuracy and excellent precision of quantitative lumen measurement in phantom models in vitro across a wide range of dimensions. Future research to confirm these findings in vivo are warranted.

Frequency-Domain Optical Coherence Tomography for Intracranial Atherosclerotic Stenosis: Feasibility, Safety, and Preliminary Experience.

Background: Despite advances in non-invasive imaging, the characterization of atherosclerotic plaque remains superior with frequency-domain optical coherence tomography (FD-OCT) in the clinical coronary and experimental cerebrovascular literature. An assessment of the feasibility and safety of FD-OCT for intracranial atherosclerotic stenosis (ICAS) is desirable.Methods: We analyzed a cohort of all consecutive FD-OCT evaluations for ICAS performed at our institution from April 2017 to August 2018 (16 months) in patients who suffered from transient ischemic attack (TIA) or non-disabling stroke despite optimal medical management within 90 days of admission attributable to angiographically verified 70–99% stenosis of an intracranial artery.Results: Thirty-three patients harboring 36 lesions with an average age of (57.6 ± 7.1) years (male sex 27 cases) comprising nine cases of lesions located within the anterior circulation and 24 cases within the posterior circulation were identified. Of the 33 patients with 36 lesions, the FD-OCT imaging catheter detected 35/36 (97%) lesions except in one case in which the FD-OCT catheter failed to navigate excessively tortuous vessels, and FD-OCT images in 27 patients (81.8%) were finally obtained successful, where the target lesion was fully visible, and image quality under at least one pullback was graded 2 or 3. There were no symptomatic complications. Blood flow was the most common artifact encountered (51.9%).Conclusion: FD-OCT is safe and feasible for the assessment of ICAS in the anterior and posterior circulation. The use of diagnostic interferometry will have to be weighed against its cost, and these preliminary findings should be verified by prospective large-scale studies.

The influence of coronary plaque morphology assessed by optical coherence tomography on final microvascular function after stenting in patients with ST-elevation myocardial infarction.

The index of microcirculatory resistance (IMR) provides a reproducible assessment of the status of coronary microvasculature in patients with ST-elevation myocardial infarction (STEMI). Frequency-domain optical coherence tomography (FD-OCT) enables detailed assessment of the morphology of coronary plaque.We sought to determine the influence of the initial culprit coronary plaque anatomy within the infarct-related artery on IMR after stenting in STEMI. In 25 STEMI patients IMR was measured immediately before and after stent implantation. FD-OCT imaging was performed at the same time points and atherothrombotic volume (ATV) before stenting, prolapsed+floating ATV after stenting and ΔATV was measured using three different strategies. There were no relationships between preprocedural IMR and FD-OCT parameters. Prestenting IMR was related only to pain to wire time (P: 0.02). Irrespective of the method adopted, the final IMR was related to prestenting ATV (ρ: 0.44, P: 0.03 for method I, ρ: 0.48, P: 0.02 for method II and ρ: 0.30, P: 0.06 for method III) and ΔATV (ρ: 0.41, P: 0.04 for method II and ρ: 0.44, P: 0.03 for method III). IMR measured before stenting is independent of the appearances of the culprit coronary plaque within the infarct-related artery. IMR after stenting, and more importantly, the change in IMR after stenting, reflect the degree of distal embolization during stent implantation.

Abstract 17829: Frequency-domain Optical Coherence Tomography Findings of Population With High Skin Auto Fluorescence

Objective: We aim to assess the coronary artery plaque features in patients with high skin auto fluorescence (SAF) using frequency-domain optical coherence tomography (FD-OCT). Background: SAF, a non-invasive measurement of the accumulation for glycation end products (AGEs) level of skin, has been reported as a useful marker for micro/macro vascular complications. Moreover patients involved with coronary artery disease (CAD) with higher SAF show worse clinical outcome compared to patients with lower SAF. Due to its unprecedented high resolution (~10μm axial), optical coherence tomography (OCT) has been increasingly used for plaque assessments. In this situation, there is no data evaluating the OCT findings of high SAF population. Methods: We prospectively enrolled 108 consecutive patients with de novo coronary artery disease underwent percutaneous coronary intervention (PCI) with FD-OCT images at pre-PCI. SAF was measured before PCI procedure. We divided the population into two group high SAF group (greater than or equal to 2.6) and low SAF group (less than 2.6), then compared FD-OCT findings between high and low SAF group. Furthermore we evaluated the predictor of thin cap fibroatheroma (TCFA) and plaque rapture by FD-OCT. Results: High SAF group shows much more TCFA and plaque rapture compared to low SAF group (63.9% vs 31.9%, p&lt;0.001 and 32.8% vs 12.8%, p&lt;0.001, respectively). In multivariable analysis, age (odds ratio [OR]: 0.96; 95% confidence interval [CI]: 0.92 to 1.00; p = 0.046) and SAF (&lt;2.6 as reference) (odds ratio [OR]: 5.89; 95% confidence interval [CI]: 2.39 to 14.51; p &lt; 0.001) were considered to be the predictor of TCFA and SAF (odds ratio [OR]: 4.23; 95% confidence interval [CI]: 1.23 to 14.51; p = 0.022), gender (male as reference) (odds ratio [OR]: 0.12; 95% confidence interval [CI]: 0.03 to 0.56; p = 0.007) and LDL (odds ratio [OR]: 1.2; 95% confidence interval [CI]: 1.02 to 1.42; p = 0.029) were considered to be the predictor of plaque rapture. Conclusion: Based on FD-OCT imaging, high SAF group shows the association with TCFA and plaque rapture compared to low SAF group. These OCT findings may explain the worse clinical outcomes of high SAF patients.

Plaque microstructures in patients with coronary artery disease who achieved very low low-density lipoprotein cholesterol levels

ObjectiveLowering low-density lipoprotein cholesterol (LDL-C) with statins reduces cardiovascular events and slows plaque progression. While this therapeutic approach has been reported to favorably modify plaque composition, this is not well characterized in humans. Also, the benefit of achieving LDL-C levels below current recommended targets remains unknown. Frequency-domain optical coherence tomography (FD-OCT) enables visualization of plaque microstructures associated with plaque instability. We investigated plaque morphologies in patients with low LDL-C levels by using FD-OCT. Methods293 and 122 non-obstructive lipid and fibrous plaques in 280 stable statin-treated CAD patients were evaluated by FD-OCT imaging in vessels requiring percutaneous coronary intervention. Study subjects were stratified according to achieved LDL-C levels (<50, 50–70, 70–100, <100 mg/dL). FD-OCT derived plaque microstructures were compared. ResultsLDL-C levels <50 mg/dL and <70 mg/dL were observed in 13.9% (39/280) and 29.2% (82/280) of patients, respectively. Patients with LDL-C <50 mg/dL were more likely to be older (p < 0.001) and receive a high-dose statin (p = 0.01). On FD-OCT imaging, patients with LDL-C <50 mg/dL were more likely to have fibrous plaque (51.7, 43.2, 22.2 and 12.3%, p = 0.01) and less likely to have lipid plaques (48.2, 56.7, 77.7 and 87.6%, p = 0.01). In addition, LDL-C level was significantly associated with lipid arc (173 ± 76, 175 ± 88, 196 ± 102 and 234 ± 85°, p = 0.01) and fibrous cap thickness (139.9 ± 93.9, 103.1 ± 66.4, 92.5 ± 48.5 and 92.1 ± 47.8 um, p = 0.001). In particular, the smallest lipid arc and thickest fibrous cap were observed in patients who achieved LDL-C <50 mg/dL. Multivariable analysis revealed LDL-C levels (beta coefficient −0.254, p = 0.009) and high-dose statin use (beta coefficient 1.814, p = 0.003) to independently associate with fibrous cap thickness. ConclusionsMore stable plaque features were observed within non-obstructive atheromas in patients with very low LDL-C levels. These findings underscore LDL-C level to stabilize plaques in patients with CAD and high residual atherosclerotic risk.

Plaque vulnerability at non-culprit lesions in obese patients with coronary artery disease: Frequency-domain optical coherence tomography analysis.

Obesity is associated with adverse atherosclerotic cardiovascular events. While various metabolic abnormalities associated with obesity promote plaque formation, the morphological phenotype of atherosclerotic plaque has not been well characterized in the setting of obesity. Frequency-domain optical coherence tomography (FD-OCT) enables invivo visualization of plaque microstructures associated with vulnerability. We characterized plaque microstructures in obese patients. FD-OCT imaging was performed in 308 patients with coronary artery disease undergoing percutaneous coronary intervention. Patients were stratified according to the presence or absence of obesity (body mass index > 30 kg/m(2)). Plaques in obese (n = 129) and non-obese (n = 179) patients were compared with regard to clinical characteristics and FD-OCT-derived features of plaque vulnerability. Obese patients were more likely to be younger (p = 0.01), female (p = 0.01) and have a history of hypertension (p = 0.01). Higher levels of triglyceride (p < 0.0001) and glucose (p = 0.02), whereas a lower level of high-density lipoprotein cholesterol (HDL-C) (p = 0.02) was observed in obese patients. FD-OCT imaging demonstrated thinner fibrous caps (85.3 ± 31.1 vs 110.1 ± 32.4 µm, p = 0.01) and a higher prevalence of thin-cap fibroatheroma (28.8 vs 14.3%, p = 0.01) in obese patients, which remained significant after controlling for differences in clinical characteristics. Achieving a low-density lipoprotein cholesterol (LDL-C) level < 1.8 mmol/l was associated with thicker fibrous caps in obese patients, but only to the level observed in non-obese patients with suboptimal lipid control. Obese patients harbor more vulnerable plaques in association with atherogenic risk factors. The limited benefit of lipid control suggests the need to adopt novel anti-atherosclerotic strategies in higher-risk patients.

Current research of acute zonal occult outer retinopathy

Acute zonal occult outer retinopathy (AZOOR) is a relatively rare ocular disease that is characterized by the rapid loss of one or more zones of outer retinal function. AZOOR usually occurs in young women. AZOOR patients typically present with the sudden onset of photopsia and acute scotomas related to loss of sectors of outer retinal function. Early in the course of AZOOR, funduscopic appearance was often normal; however, most patients developed zones of retinal pigment epithelial atrophy or pigment clumping over time. Changes in electroretinogram (ERG) and persistent visual field defects were usually observed. Optical coherence tomography (OCT) showed that inner segment (IS)/outer segment (OS) regional abnormal changes corresponding to the visual field defect location area, at the same time the morphology and position of the visual field defect and multifocal electroretinogram (mfERG) shown in retinal amplitude density decreased regions coincide. The visual function of some patients can permanently damage. Fundus examination, mfERG and fluorescein angiography (FA), indocyanine green angiography (ICGA), autofluorescence (AF) and frequency domain OCT imaging techniques has an important significance for the diagnosis of AZOOR. Ever since the lack of understanding, AZOOR is often missed or misdiagnosed. In order to improve the understanding of the disease, this paper reviewed the definition, etiology, the epidemiological characteristics, clinical manifestation, classification, diagnosis, differential diagnosis, treatment and prognosis of AZOOR. Key words: Acute zonal occult outer retinopathy; Retinal diseases; Photopsia; Scotomas

GPU-accelerated framework for intracoronary optical coherence tomography imaging at the push of a button.

Frequency domain optical coherence tomography (FD-OCT) has become one of the important clinical tools for intracoronary imaging to diagnose and monitor coronary artery disease, which has been one of the leading causes of death. To help more accurate diagnosis and monitoring of the disease, many researchers have recently worked on visualization of various coronary microscopic features including stent struts by constructing three-dimensional (3D) volumetric rendering from series of cross-sectional intracoronary FD-OCT images. In this paper, we present the first, to our knowledge, "push-of-a-button" graphics processing unit (GPU)-accelerated framework for intracoronary OCT imaging. Our framework visualizes 3D microstructures of the vessel wall with stent struts from raw binary OCT data acquired by the system digitizer as one seamless process. The framework reports the state-of-the-art performance; from raw OCT data, it takes 4.7 seconds to provide 3D visualization of a 5-cm-long coronary artery (of size 1600 samples x 1024 A-lines x 260 frames) with stent struts and detection of malapposition automatically at the single push of a button.

A honeycomb-like structure in chronic total occlusion demonstrated by frequency-domain optical coherence tomography

A 68 year-old male with a history of hypertension and current smoking was admitted due to exertional chest pain. Coronary angiography (CAG) showed a chronic total occlusion (CTO) in the left circumflex artery with collateral supply from the right coronary artery (Fig. 1). PCI was performed in this lesion as patient has normal left ventricular function. After crossing the lesion with a guide wire (Gaia 2nd) and micro catheter, frequency-domain optical coherence tomography (FD-OCT) (ILUMIEN™ OCT Imaging System, St Jude Medical, Inc, St Paul, Minnesota) was performed. FD-OCT showed fibrous/calcified plaque and white thrombus (Fig. 2C–E ). Furthermore FD-OCT showed a honeycomb-like structure (Fig. 2B) at the proximal part of the entry site of the CTO lesion. After balloon angioplasty, this lesion was treated with everolimus-eluting stent (EES 3.0 × 38 mm/2.5 × 18 mm, Xience Xpedition, Abbott Vascular, Santa Clara, California) implantation (Fig. 3). Fig. 2Coronary angiogram and FD-OCT images of LCX CTO lesion after guide wire crossing. Show full caption Coronary angiogram shows the CTO lesion after guide wire crossing. Red dotted line shows the CTO lesion. Yellow dotted lines correspond to the FD-OCT cross sectional images. FD-OCT shows the fibrous and calcified plaque (A) in non-CTO lesion. At the proximal lesion very close to the CTO entry site, FD-OCT shows a honeycomb-like structure (B). Panels C–E show the fibrous and calcified plaque (red arrows) with white thrombus (white arrows) in the CTO lesion. Panel F shows the fibrotic plaque in non-CTO lesion. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) View Large Image Figure Viewer Download Hi-res image Fig. 3Coronary angiogram image of LCX after EES implantation. Show full caption Angiogram shows good stent expansion after EES implantation (3.0 × 38 mm/2.5 × 18 mm). View Large Image Figure Viewer Download Hi-res image Coronary angiogram shows the CTO lesion after guide wire crossing. Red dotted line shows the CTO lesion. Yellow dotted lines correspond to the FD-OCT cross sectional images. FD-OCT shows the fibrous and calcified plaque (A) in non-CTO lesion. At the proximal lesion very close to the CTO entry site, FD-OCT shows a honeycomb-like structure (B). Panels C–E show the fibrous and calcified plaque (red arrows) with white thrombus (white arrows) in the CTO lesion. Panel F shows the fibrotic plaque in non-CTO lesion. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Angiogram shows good stent expansion after EES implantation (3.0 × 38 mm/2.5 × 18 mm).

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

ObjectivesThe 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 & resultsA 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±0.55ml/s as compared to 4.81±1.95ml/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. ConclusionThe 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).

Frequency-Domain Optical Coherence Tomographic Analysis of Plaque Microstructures at Nonculprit Narrowings in Patients Receiving Potent Statin Therapy

Potent statin therapy has been demonstrated to reduce cardiovascular events. Although statins have been considered to stabilize atherosclerotic plaque, this effect has not been well characterized invivo. We investigated the relation between potent statin therapy and plaque microstructures imaged by frequency-domain optical coherence tomography. Two hundred ninety nonculprit lipid plaques in 275 patients with stable coronary artery disease receiving atorvastatin or rosuvastatin were analyzed. Patients were stratified into no statin, low-, and high-dose statin groups. Plaques in the high-dose statin group demonstrated a smaller lipid arc (p= 0.02) and a greater fibrous cap thickness (p= 0.01). In patients receiving statin therapy, high-dose statin therapy was associated with a greater fibrous cap thickness in patients with smaller (148.2 ± 30.5 vs 105.3 ± 41.1 μm, p= 0.004) but not larger lipid index (91.1 ± 32.6 vs 78.1 ± 43.3 μm, p= 0.21). In conclusion, potent statin therapy is associated with less vulnerable plaque features on frequency-domain optical coherence tomography imaging. This finding varies according to the size of plaque lipid content, being less effective in lipid-loaded plaques.

Side branch complication after a single-stent crossover technique: prediction with frequency domain optical coherence tomography.

To identify preprocedural predictors of side branch (SB) complications after coronary bifurcation stent implantation using frequency domain optical coherence tomography (FD-OCT). Coronary bifurcation lesions are common but difficult to treat. Longitudinal reconstruction images of FD-OCT have high image quality and less motion artifacts. Among 49 patients (age: 69.9 years) who underwent elective coronary stenting, 52 bifurcation lesions without baseline SB stenosis were studied. SB complication was defined as angiographic worsening of SB stenosis (>75%). On the basis of preprocedural FD-OCT imaging, plaque distribution, SB angle, carina tip angle (CT angle), and length between proximal branching point to carina tip (BP-CT length) were evaluated. SB complication was observed in 22 lesions. The eccentric plaque distribution oriented toward the opposite side of SB at the CT was significantly more frequent in lesions with SB complication compared with those without (77.3 vs. 16.7%, P<0.01). CT angle and BP-CT length were significantly smaller in lesions with SB complication compared with those without [29.5° (interquartile range (IQR) 22.3-44.3°) vs. 65.0° (IQR 42.5-90.0°)], P<0.001; 1.20 mm (IQR 0.70-1.73 mm) vs. 2.25 mm (IQR 1.78-3.20 mm), P<0.001, respectively]. The receiver-operating characteristic curve indicated a CT angle less than 50° (area under the curve=0.81, sensitivity 86%, specificity 70%) and BP-CT length less than 1.70 mm (area under the curve=0.84, sensitivity 77%, specificity 77%) as the best cutoff values for predicting the SB complication after main vessel stent implantation. This FD-OCT study showed that narrower CT angle and shorter BP-CT length were the independent predictors for SB complications after bifurcation stenting.

Frequency‐domain optical coherence tomography assessment of unprotected left main coronary artery disease—a comparison with intravascular ultrasound

To investigate safety and feasibility of imaging unprotected left main (ULM) using frequency-domain optical coherence tomography (FD-OCT) compared with intravascular ultrasound (IVUS). IVUS has been used to assess and guide percutaneous coronary intervention (PCI) of ULM disease. FD-OCT offers 10-fold higher axial resolution than IVUS and its high-speed image acquisition obviates the need for proximal balloon occlusion. We prospectively enrolled 35 consecutive patients with ULM disease. FD-OCT and IVUS assessments were attempted pre- and post-PCI and compared in regards to safety, ability to image the region of interest (ROI), number of pullbacks, volume of contrast and ability to detect malapposition, dissection, and thrombus. Patients were followed for 1 year when FD-OCT imaging was repeated. FD-OCT required more repeated pullbacks to image the ROI compared to IVUS. Mean lumen and stent areas were similar between FD-OCT and IVUS (11.24 ± 2.66 vs. 10.85 ± 2.47 mm(2) , P = 0.13 and 10.44 ± 2.33 vs. 10.49 ± 2.32 mm(2) , P = 0.82, respectively), whereas imaged stent length was shorter with FD-OCT. Malapposition areas and volumes were larger and more edge dissections were detected by FD-OCT. There were no clinical adverse events and no complications associated with FD-OCT at baseline and 1-year follow-up. All dissections were healed, whereas stent malapposition was still detected at follow-up. FD-OCT assessment of ULM is feasible and safe. Direct comparisons with IVUS reveal that FD-OCT achieved imaging completeness less often, whereas it was more sensitive in detecting malapposition and edge dissections, and similar to IVUS in the assessment of lumen and stent dimensions.

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

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. 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). 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.

Evaluation of Below-the-Knee Drug-Eluting Stents With Frequency-Domain Optical Coherence Tomography: Neointimal Hyperplasia and Neoatherosclerosis

To report the use of intravascular frequency-domain optical coherence tomography (FD-OCT) to detect and characterize in-stent neointimal tissue following infrapopliteal drug-eluting stent (DES) placement in patients suffering from critical limb ischemia. This prospective study included 12 patients (7 men; mean age 72.8±7.2 years) who had previously received 21 infrapopliteal sirolimus- or everolimus-eluting stents. The patients returned for regular angiographic follow-up or presented with clinical relapse of symptoms over a mean follow-up of 13.5±7.3 months (range 6-33), at which time FD-OCT imaging was performed. Study endpoints were technical imaging success, defined as successful FD-OCT acquisition and visualization of the arterial lumen and complete vessel wall, and the detection and characterization of in-stent neointimal hyperplasia according to widely accepted OCT criteria. OCT imaging was successfully completed in 19 of the 21 stents. Binary in-stent restenosis (ISR>50%) was detected in 10/19 stents. Percent restenosis was higher after longer follow-up (60.6%±19.8% ≥1 year vs. 35.3%±20.6% <1 year, p=0.03) and in symptomatic vs. asymptomatic patients (61.5%±20.4% vs. 37.2%±19.3%, p=0.04). Neoatherosclerosis findings included lipid-laden neointima (16/19), neointimal neovascularization (13/19), neointimal calcifications (6/19), and thrombus (5/19); no cases of thin-cap fibroatheroma were identified. Neointimal calcifications were more frequent after ≥12 months of follow-up compared to <12 months (46.6% vs. 0%, p=0.02). FD-OCT of the infrapopliteal arteries following DES placement is safe and feasible and may demonstrate features of developing neointimal neoatherosclerosis. The latter might play a key role as a mechanism of below-the-knee ISR and warrants further investigation.

Volumetric Characterization of Human Coronary Calcification by Frequency-Domain Optical Coherence Tomography

Coronary artery calcification (CAC) presents unique challenges for percutaneous coronary intervention. Calcium appears as a signal-poor region with well-defined borders by frequency-domain optical coherence tomography (FD-OCT). The objective of this study was to demonstrate the accuracy of intravascular FD-OCT to determine the distribution of CAC. Cadaveric coronary arteries were imaged using FD-OCT at 100-μm frame interval. Arteries were subsequently frozen, sectioned and imaged at 20-μm intervals using the Case Cryo-Imaging automated system(TM). Full volumetric co-registration between FD-OCT and cryo-imaging was performed. Calcium area, calcium-lumen distance (depth) and calcium angle were traced on every cross-section; volumetric quantification was performed offline. In total, 30 left anterior descending arteries were imaged: 13 vessels had a total of 55 plaques with calcification by cryo-imaging; FD-OCT identified 47 (85%) of these plaques. A total of 1,285 cryo-images were analyzed and compared with corresponding co-registered 257 FD-OCT images. Calcium distribution, represented by the mean depth and the mean calcium angle, was similar, with excellent correlation between FD-OCT and cryo-imaging respectively (mean depth: 0.25±0.09 vs. 0.26±0.12mm, P=0.742; R=0.90), (mean angle: 35.33±21.86° vs. 39.68±26.61°, P=0.207; R=0.90). Calcium volume was underestimated in large calcifications (3.11±2.14 vs. 4.58±3.39mm(3), P=0.001) in OCT vs. cryo respectively. Intravascular FD-OCT can accurately characterize CAC distribution. OCT can quantify absolute calcium volume, but may underestimate calcium burden in large plaques with poorly defined abluminal borders.