Stent detection with very thick tissue coverage in intravascular OCT.

Coronary stenting or percutaneous coronary intervention (PCI) is widely used to treat coronary artery disease. Improper deployment of stents may lead to post-PCI complication, in-stent restenosis, stent fracture and stent thrombosis. Intravascular optical coherence tomography (OCT) with micron-scale resolution provides accurate in vivo assessment of stent apposition/malapposition and neointima coverage. However, manual stent analysis is labor intensive and time consuming. Existing automated methods with intravascular OCT mainly focused on stent struts with thin tissue coverage. We developed a deep learning method to automatically analyze stents with both thin (≤0.3mm) and very thick tissue coverage (>0.3mm), and an algorithm to accurately analyze stent area for vessels with multiple stents. 25203 images from 56 OCT pullbacks and 41 patients were analyzed. Three-fold cross-validation demonstrated that the algorithm achieved a precision of 0.932±0.009 and a sensitivity of 0.939±0.007 for stents with ≤0.3mm tissue coverage, and a precision of 0.856±0.019 and a sensitivity of 0.874±0.011 for stents with >0.3mm tissue coverage. The correlation between the automatically computed and manually measured stent area is 0.954 (p<0.0001) for vessels with a single stent, and is 0.918 (p<0.0001) for vessels implanted with multiple stents. The proposed method can accurately detect stent struts with very thick tissue coverage and analyze stent area in vessels implanted with multiple stents, and can effectively facilitate the evaluation of stent implantation and post-stent tissue coverage.

Automated A-line coronary plaque classification of intravascular optical coherence tomography images using handcrafted features and large datasets.

We developed machine learning methods to identify fibrolipidic and fibrocalcific A-lines in intravascular optical coherence tomography (IVOCT) images using a comprehensive set of handcrafted features. We incorporated features developed in previous studies (e.g., optical attenuation and A-line peaks). In addition, we included vascular lumen morphology and three-dimensional (3-D) digital edge and texture features. Classification methods were developed using expansive datasets (∼7000 images), consisting of both clinical in-vivo images and an ex-vivo dataset, which was validated using 3-D cryo-imaging/histology. Conditional random field was used to perform 3-D classification noise cleaning of classification results. We tested various multiclass approaches, classifiers, and feature selection schemes and found that a three-class support vector machine with minimal-redundancy-maximal-relevance feature selection gave the best performance. We found that inclusion of our morphological and 3-D features improved overall classification accuracy. On a held-out test set consisting of >1700 images, we obtained an overall accuracy of 81.58%, with the following (sensitivity/specificity) for each class: other (81.43/89.59), fibrolipidic (94.48/87.32), and fibrocalcific (74.82/95.28). The en-face views of classification results showed that automated classification easily captured the preponderance of a disease segment (e.g., a calcified segment had large regions of fibrocalcific classifications). Finally, we demonstrated proof-of-concept for streamlining A-line classification output with existing fibrolipidic and fibrocalcific boundary segmentation methods, to enable fully automated plaque quantification. The results suggest that our classification approach is a viable step toward fully automated IVOCT plaque classification and segmentation for live-time treatment planning and for offline assessment of drug and biologic therapeutics.

Troponin Improves the Yield of Transthoracic Echocardiography in Ischemic Stroke Patients of Determined Stroke Subtype.

Background and Purpose- Transthoracic echocardiography (TTE) is widely used in the ischemic stroke setting. In this study, we aim to investigate the yield of TTE in patients with ischemic stroke and known subtype and whether the admission troponin level improves the yield of TTE. Methods- Data were abstracted from a single-center prospective ischemic stroke database for 18 months and included all patients with ischemic stroke whose etiologic subtype could be obtained without the need of TTE. Unadjusted and adjusted regression models were built to determine whether positive cardiac troponin levels (≥0.1 ng/mL) improve the yield of TTE, adjusting for demographic and clinical characteristics. Results- We identified 578 patients who met the inclusion criteria. TTE changed clinical management in 64 patients (11.1%), but intracardiac thrombus was detected in only 4 patients (0.7%). In multivariable models, there was an association between TTE changing management and positive serum troponin level (adjusted odds ratio, 4.26; 95% CI, 2.17-8.34; P<0.001). Conclusions- In patients with ischemic stroke, TTE might lead to a change in clinical management in ≈1 of 10 patients with known stroke subtype before TTE but changed acute treatment decisions in <1 percent of patients. Serum troponin levels improved the yield of TTE in these patients.

A Simple Score That Predicts Paroxysmal Atrial Fibrillation on Outpatient Cardiac Monitoring after Embolic Stroke of Unknown Source.

BACKGROUND: Occult paroxysmal atrial fibrillation (AF) is detected in 16%-30% of patients with embolic stroke of unknown source (ESUS). The identification of AF predictors on outpatient cardiac monitoring can help guide clinicians decide on a duration or method of cardiac monitoring after ESUS. METHODS: We included all patients with ESUS who underwent an inpatient diagnostic evaluation and outpatient cardiac monitoring between January 1, 2013, and December 31, 2016. Patients were divided into 2 groups based on detection of AF or atrial flutter during monitoring. We compared demographic data, clinical risk factors, and cardiac biomarkers between the 2 groups. Multivariable logistic regression was used to determine predictors of AF. RESULTS: We identified 296 consecutive patients during the study period; 38 (12.8%) patients had AF detected on outpatient cardiac monitoring. In a multivariable regression analysis, advanced age (ages 65-74: odds ratio [OR] 2.36, 95% confidence interval [CI] .85-6.52; ages 75 or older: OR 4.08, 95% CI 1.58-10.52) and moderate-to-severe left atrial enlargement (OR 4.66, 95% CI 1.79-12.12) were predictors of AF on outpatient monitoring. We developed the Brown ESUS-AF score: age (65-74 years: 1 point, 75 years or older: 2 points) and left atrial enlargement (moderate or severe: 2 points) with good prediction of AF (area under the curve .725) and was internally validated using bootstrapping. The percentage of patients with AF detected in each score category were as follows: 0: 4.2%; 1: 14.8%; 2: 20.8%; 3: 22.2%; 4: 55.6%. CONCLUSIONS: The Brown ESUS-AF score predicts AF on prolonged outpatient monitoring after ESUS. More studies are needed to externally validate our findings.

Early Elevated Troponin Levels After Ischemic Stroke Suggests a Cardioembolic Source.

BACKGROUND AND PURPOSE: Elevated cardiac troponin is a marker of cardiac disease and has been recently shown to be associated with embolic stroke risk. We hypothesize that early elevated troponin levels in the acute stroke setting are more prevalent in patients with embolic stroke subtypes (cardioembolic and embolic stroke of unknown source) as opposed to noncardioembolic subtypes (large-vessel disease, small-vessel disease, and other). METHODS: We abstracted data from our prospective ischemic stroke database and included all patients with ischemic stroke during an 18-month period. Per our laboratory, we defined positive troponin as ≥0.1 ng/mL and intermediate as ≥0.06 ng/mL and <0.1 ng/mL. Unadjusted and adjusted regression models were built to determine the association between stroke subtype (embolic stroke of unknown source and cardioembolic subtypes) and positive and intermediate troponin levels, adjusting for key confounders, including demographics (age and sex), clinical characteristics (hypertension, hyperlipidemia, diabetes mellitus, renal function, coronary heart disease, congestive heart failure, current smoking, and National Institutes of Health Stroke Scale score), cardiac variables (left atrial diameter, wall-motion abnormalities, ejection fraction, and PR interval on ECG), and insular involvement of infarct. RESULTS: We identified 1234 patients, of whom 1129 had admission troponin levels available; 10.0% (113/1129) of these had a positive troponin. In fully adjusted models, there was an association between troponin positivity and embolic stroke of unknown source subtype (adjusted odds ratio, 4.46; 95% confidence interval, 1.03-7.97; P=0.003) and cardioembolic stroke subtype (odds ratio, 5.00; 95% confidence interval, 1.83-13.63; P=0.002). CONCLUSIONS: We found that early positive troponin after ischemic stroke may be independently associated with a cardiac embolic source. Future studies are needed to confirm our findings using high-sensitivity troponin assays and to test optimal secondary prevention strategies in patients with embolic stroke of unknown source and positive troponin.

Use of cardiovascular magnetic resonance in the evaluation of a giant right atrial appendage aneurysm: a case report and review of the literature.

BACKGROUND: Right atrial appendage aneurysms are rare entities that may have significant clinical consequences. When co-existing with atrial fibrillation, patients are at risk of developing pulmonary or paradoxical systemic emboli. CASE PRESENTATION: An elderly patient presented to medical attention with symptoms of acute diverticulitis. On abdominal computed tomography, a massively enlarged right atrial appendage aneurysm was discovered incidentally. The aneurysm caused marked compression of the right ventricle and contained an area of hypoenhancement concerning for an intraluminal thrombus. Gadolinium-enhanced cardiovascular magnetic resonance was performed and first-pass perfusion images demonstrated that the area of hypoenhancement was in fact poorly mixing blood. The patient was therefore managed medically. CONCLUSION: Right atrial appendage aneurysms are infrequently encountered cardiac abnormalities. In the literature, surgery has been offered to patients who are young, symptomatic, or have evidence of thrombotic disease, although whether this practice pattern is associated with superior clinical outcomes is unclear. In the present case, gadolinium-enhanced cardiovascular magnetic resonance imaging was used to exclude the presence of intraluminal thrombus in an elderly patient, which helped orient the patient's treating team towards medical-rather than surgical-therapy.

Vulnerable plaques, more than meets the i.

Intravascular imaging plays a key role in the identification of mechanisms of acute coronary syndromes Post processing IVUS algorithms (IMAP-IVUS and VH-IVUS) for tissue characterization have not been widely adopted due to current limitations Future development will allow easier, faster, and more accurate identification of vulnerable plaques, ultimately allowing prognostication of various interventions.

Failure Mechanisms and Neoatherosclerosis Patterns in Very Late Drug-Eluting and Bare-Metal Stent Thrombosis.

BACKGROUND: There are few clinical studies on the pathophysiological mechanisms of very late stent thrombosis (VLST). We report optical coherence tomography findings in patients with VLST and compare the findings between bare-metal stents (BMS) and drug-eluting stents (DES). METHODS AND RESULTS: We conducted a registry of stent thrombosis at 4 North American centers with optical coherence tomography imaging programs SAFE registry (The Study of Late Stent Failure Evaluated by OCT). Images were acquired in 61 patients (42 DES and 19 BMS) presenting with definite VLST. The median duration from implantation to VLST presentation was 51.4 months in the DES and 69.9 months in the BMS group (P=0.011). Uncovered and malapposed struts were observed in 70.5% (43/61) and 62.3% (38/61) of patients, respectively, whereas neoatherosclerosis was revealed in 49.2% (30/61). Stent underexpansion was observed in 42.4% of patients. Malapposed struts and stent underexpansion were more frequently demonstrated in DES than in BMS patients, whereas neoatherosclerosis was frequently observed in BMS (40.5% in DES and 68.4% in BMS; P=0.056). The percentage of frames with neoatherosclerosis was lower in DES than in BMS (15.56% [12.24-28.57] versus, 56.41% [40.74-70.00], respectively; P<0.001). Maximum consecutive lipid neointima length was shorter in DES than in BMS (2.4 [1.2-3.6] and 5.3 [3.0-7.0] mm; P=0.011). CONCLUSIONS: Optical coherence tomography imaging demonstrated that VLST in DES and BMS had a wide variety of abnormal findings, such as neoatherosclerosis, uncovered strut, and malapposed strut. Neoatherosclerosis and lipid neointima were more frequently observed and had more longitudinal extension in BMS compared with DES.

Three-dimensional registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation.

Evidence suggests high-resolution, high-contrast, [Formula: see text] intravascular optical coherence tomography (IVOCT) can distinguish plaque types, but further validation is needed, especially for automated plaque characterization. We developed experimental and three-dimensional (3-D) registration methods to provide validation of IVOCT pullback volumes using microscopic, color, and fluorescent cryo-image volumes with optional registered cryo-histology. A specialized registration method matched IVOCT pullback images acquired in the catheter reference frame to a true 3-D cryo-image volume. Briefly, an 11-parameter registration model including a polynomial virtual catheter was initialized within the cryo-image volume, and perpendicular images were extracted, mimicking IVOCT image acquisition. Virtual catheter parameters were optimized to maximize cryo and IVOCT lumen overlap. Multiple assessments suggested that the registration error was better than the [Formula: see text] spacing between IVOCT image frames. Tests on a digital synthetic phantom gave a registration error of only [Formula: see text] (signed distance). Visual assessment of randomly presented nearby frames suggested registration accuracy within 1 IVOCT frame interval ([Formula: see text]). This would eliminate potential misinterpretations confronted by the typical histological approaches to validation, with estimated 1-mm errors. The method can be used to create annotated datasets and automated plaque classification methods and can be extended to other intravascular imaging modalities.

Impact of Neointimal Calcifications on Acute Stent Performance during the Treatment of In-Stent Restenosis.

Optical coherence tomography (OCT) has become the invasive imaging modality of choice for coronary stent assessment due to its unmatched spatial resolution. Neointimal calcification (NC) is a rare finding, observed in 5-10% of in-stent restenosis (ISR) neointima. The impact of NC on percutaneous coronary intervention of ISR is unknown. We therefore present the outcome of six unique cases of ISR and NC in which OCT was used to evaluate the impact of NC on the quality of stent-in-stent deployment for the treatment of ISR. This series demonstrates for the first time the impact of NC on stent expansion, a finding which might help guiding percutaneous coronary intervention for ISR with NC.

3D registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation.

High resolution, 100 frames/sec intravascular optical coherence tomography (IVOCT) can distinguish plaque types, but further validation is needed, especially for automated plaque characterization. We developed experimental and 3D registration methods, to provide validation of IVOCT pullback volumes using microscopic, brightfield and fluorescent cryo-image volumes, with optional, exactly registered cryo-histology. The innovation was a method to match an IVOCT pull-back images, acquired in the catheter reference frame, to a true 3D cryo-image volume. Briefly, an 11-parameter, polynomial virtual catheter was initialized within the cryo-image volume, and perpendicular images were extracted, mimicking IVOCT image acquisition. Virtual catheter parameters were optimized to maximize cryo and IVOCT lumen overlap. Local minima were possible, but when we started within reasonable ranges, every one of 24 digital phantom cases converged to a good solution with a registration error of only +1.34±2.65µm (signed distance). Registration was applied to 10 ex-vivo cadaver coronary arteries (LADs), resulting in 10 registered cryo and IVOCT volumes yielding a total of 421 registered 2D-image pairs. Image overlays demonstrated high continuity between vascular and plaque features. Bland-Altman analysis comparing cryo and IVOCT lumen area, showed mean and standard deviation of differences as 0.01±0.43 mm2. DICE coefficients were 0.91±0.04. Finally, visual assessment on 20 representative cases with easily identifiable features suggested registration accuracy within one frame of IVOCT (±200µm), eliminating significant misinterpretations introduced by 1mm errors in the literature. The method will provide 3D data for training of IVOCT plaque algorithms and can be used for validation of other intravascular imaging modalities.

Heart failure in patients with human immunodeficiency virus infection: Epidemiology and management disparities.

BACKGROUND: Persons living with HIV are at a higher risk of cardiovascular disease despite effective antiretroviral therapy and dramatic reductions in AIDS-related conditions. We sought to identify the epidemiology of heart failure (HF) among persons living with HIV in the United States in an era of contemporary antiretroviral therapy. METHODS: Explorys is an electronic healthcare database that aggregates medical records from 23 healthcare systems nationwide. Using systemized nomenclature of medicine-clinical terms (SNOMED-CT), we identified adult patients (age>18), who had active records over the past year (September 2014-September 2015). We described the prevalence of HF in HIV patients by demographics and treatment and compared them to HIV-uninfected controls. RESULTS: Overall, there were 36,400 patients with HIV and 12,208,430 controls. The overall prevalence of HF was 7.2% in HIV and 4.4% in controls (RR 1.66 [1.60-1.72], p<0.0001). The relative risk of HF associated with HIV infection was higher among women and younger age groups. Patients receiving antiretroviral therapy had only marginally lower risk (6.4% vs. 7.7%, p<0.0001) of HF compared to those who were untreated. Compared to uninfected patients with HF, HIV patients with HF were less likely to receive antiplatelet drugs, statins, diuretics, and ACE/ARBs (p<0.0001 for all comparisons). For patients with HIV and HF, receiving care from a cardiologist was associated with higher use of antiplatelets, statins, betablockers, ACE/ARBs, and diuretics. CONCLUSIONS: Persons with HIV are at higher risk for HF in this large contemporary sample that includes both men and women. Although the prevalence of heart failure is higher in older HIV patients, the relative risk associated with HIV is highest in young people and in women. HIV patients are less likely to have HF optimally treated, but cardiology referral was associated with higher treatment rates.

Cardiorespiratory Fitness and Atherosclerosis: Recent Data and Future Directions.

Historically, the relationship between exercise and the cardiovascular system was viewed as unidirectional, with a disease resulting in exercise limitation and hazard. This article reviews and explores the bidirectional nature, delineating the effects, generally positive, on the cardiovascular system and atherosclerosis. Exercise augments eNOS, affects redox potential, and favorably affects mediators of atherosclerosis including lipids, glucose homeostasis, and inflammation. There are direct effects on the vasculature as well as indirect benefits related to exercise-induced changes in body composition and skeletal muscle. Application of aerobic exercise to specific populations is described, with the hope that this knowledge will move the science forward and improve individual patient outcome.

Restenosis of the Coronary Arteries: Past, Present, Future Directions.

Restenosis is a pathologic response to vascular injury, characterized by neointimal hyperplasia and progressive narrowing of a stented vessel segment. Although advances in stent design have led to a dramatic reduction in the incidence of restenosis, it continues to represent the most common cause of target lesion failure following percutaneous coronary intervention. Efforts to maximize restenosis prevention, through careful consideration of modifiable risk factors and an individualized approach, are critical, as restenosis, once established, can be particularly difficult to treat. Novel approaches are on the horizon that have the potential to alter the natural history of this stubborn disease.

Longitudinal Geographic Miss (LGM) in Robotic Assisted Versus Manual Percutaneous Coronary Interventions.

OBJECTIVES: To evaluate the impact of robotic-assisted percutaneous coronary intervention (RA-PCI) versus manual PCI (M-PCI) on the incidence of Longitudinal Geographic Miss (LGM). BACKGROUND: The safety and feasibility of RA-PCI has been established in preclinical animal trials and human clinical trials. Patients with LGM have been shown to have worse clinical outcomes including significantly increased incidences of MACE. METHODS: Patients with significant coronary artery disease underwent RA-PCI in the PRECISE study (n=164) and standard M-PCI in the STLLR trial (n = 1,509). Longitudinal geographic miss was defined as cases where the entire length of the injured or stenotic segment was not fully covered by the total length of the stent. The incidence of LGM was compared between RA-PCI and M-PCI cohorts. RESULTS: The RA-PCI cohort had a significantly greater prevalence of previous MI, previous coronary revascularization, and unstable angina. The robotic cohort exhibited a lower incidence of LGM when compared to the M-PCI patients, 12.2% to 43.1%, respectively (P < 0.0001). To account for the differences in baseline characteristics between the two studies, a propensity score analysis was conducted. The propensity modeling showed similar rates of LGM in both a larger group of patients that met key PRECISE study inclusion/exclusion criteria adjusted for propensity score (9.3% vs 55.0%; P < 0.0001) and in a smaller, matched on propensity score, subset of patients (10.3% vs 64.1%; P < 0.0001). CONCLUSION: Robotic-assisted PCI had significantly lower incidence of LGM compared to standard M-PCI. Reducing LGM potentially improves long-term clinical outcomes through reduction in MACE.

Serial assessment of vessel interactions after drug-eluting stent implantation in unprotected distal left main coronary artery disease using frequency-domain optical coherence tomography.

OBJECTIVES: This study sought to assess stent-vessel interactions after drug-eluting stent (DES) implantation in unprotected left main coronary artery (ULM) by frequency-domain optical coherence tomography (FD-OCT). BACKGROUND: Percutaneous coronary intervention using DES in ULM has been increasingly performed in routine practice. Recently, FD-OCT assessments of DES-vessel interactions have been used as surrogates for DES safety; however, there are no FD-OCT studies in ULM. METHODS: We prospectively enrolled 33 consecutive patients with ULM disease treated with sirolimus- (n = 11) and everolimus-eluting stents (n = 22). FD-OCT assessments were performed post-percutaneous coronary intervention and at 9-month follow-up. Three different segments of ULM were compared: distal (DIS), bifurcation (BIF), and ostial-body (BODY). The primary endpoints were percentages of uncovered and malapposed struts at 9-month follow-up, and the secondary endpoint was neointimal hyperplasia area. RESULTS: We analyzed 25,873 stent struts. Significant differences were demonstrated for percentage of uncovered struts (3.4%, 11.7%, and 18.7%, respectively for DIS, BIF, and BODY; p < 0.05 for all the comparisons). Malapposition was also more common in BODY (5.3%) than in DIS (0.6%) and BIF (2.0%) segments (p < 0.05 for BODY vs. DIS, and BODY vs. BIF). Equivalent neointimal hyperplasia areas were demonstrated in all segments. Acute malapposition rates led to different patterns of DES-vessel interactions at 9-month follow-up. CONCLUSIONS: Distinct patterns of DES-vessel interactions were demonstrated in different segments of ULM. Acute stent strut malapposition affects these findings.

Incidence, predictors, morphological characteristics, and clinical outcomes of stent edge dissections detected by optical coherence tomography.

OBJECTIVES: This study sought to investigate the frequency, predictors, and detailed qualitative and quantitative assessment of optical coherence tomography (OCT)-detected stent edge dissections. Its impact on subsequent management and clinical outcomes were also investigated. BACKGROUND: OCT is a high-resolution imaging modality that can lead to more frequent recognition and accurate assessment of vascular injuries during percutaneous coronary intervention (PCI). METHODS: From September 2010 to June 2011, all patients with OCT post-PCI were enrolled. Edge dissections were defined as disruptions of the arterial lumen surface in both the 5-mm distal and proximal stent edges. Qualitative and quantitative analyses of all edges were performed at 0.2-mm intervals. RESULTS: In total, 395 edges (249 lesions in 230 patients) were analyzed. The overall incidence of OCT-detected edge dissection was 37.8%, and most (84%) were not apparent on angiography. Independent predictors for OCT-detected dissections were presence of atherosclerotic plaque at stent edges, calcification angle, minimum fibrous cap thickness, thin-cap fibroatheromas, stent/lumen eccentricity, and vessel overstretching. Mean dissection length measured 2.04 ± 1.60 mm, 96.2% appeared as flaps, and 52.8% extended beyond the intima/atheroma layer. Additional stenting was performed in 22.6% of all dissections, which were longer, had bigger dimensions, and promoted deeper vascular injury. The 12-month major adverse cardiac event rate was similar between patients with (7.95%) and without (5.69%, p = 0.581) dissections. CONCLUSIONS: High rates of stent edge dissections were detected by OCT, usually related to the presence of atherosclerosis at stent edges and to PCI technique. Detailed OCT assessment of dissection severity was possible and affected the subsequent management of this complication. Non-flow-limiting, small, and superficial dissections left untreated proved benign.

Volumetric characterization of human coronary calcification by frequency-domain optical coherence tomography.

BACKGROUND: 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. METHODS AND RESULTS: 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. CONCLUSIONS: 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.