Emile Mehanna

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

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

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).

In vitro validation of new Fourier-domain optical coherence tomography

AIMS To validate the accuracy and evaluate the intra- and inter-observer variability of vascular measurements using novel Fourier-domain optical coherence tomography (FD-OCT) versus intravascular ultrasound (IVUS) in a coronary phantom model. METHODS AND RESULTS A dedicated cylindrical phantom comprised of four sections with differing dimensions was used to compare images generated by five FD-OCT and five IVUS catheters. Each FD-OCT catheter was tested using three different consoles, generating 15 imaging pullbacks. Two independent experts, blinded to the phantom data, performed measurements. There were 180 FD-OCT and 60 IVUS cross-sectional measurements of mean lumen diameter (MeanLD), minimal lumen diameter (MLD), maximum lumen diameter (MaxLD) and lumen area (LA) at three points in each section. FD-OCT measurements had excellent correlations with IVUS (concordance correlation coefficient [CCC]: ≥0.9769 for MeanLD, LA or longitudinal length [LL]) and phantom dimensions (CCCs for FD-OCT: ≥0.9958 for MeanLD, LA or LL). FD-OCT measurements were larger than IVUS (p<0.0001), but showed less measurement errors compared to IVUS (p<0.0001). Moreover, FD-OCT caused less discrepancy between MaxLD and MLD versus IVUS (p<0.0001). Intra- and inter-observer variability was low for both FD-OCT (CCCs for MeanLD, LA and LL ≥0.9996) and IVUS (≥0.9935). Image catheter position did not influence FD-OCT measurements. CONCLUSIONS FD-OCT was more accurate than IVUS and had similar high reproducibility to determine vascular dimensions in vitro. These results support the use of FD-OCT in the clinical setting.

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.

Imaging a spiral dissection of the superficial femoral artery in high resolution with optical coherence tomography—Seeing is believing

Optical coherence tomography (OCT) offers an alternative to intravascular ultrasound (IVUS) for endovascular imaging. Clinical and research applications for OCT have emerged in percutaneous coronary intervention (PCI), however, OCT has not found similar utility in peripheral arterial interventions. Early generation time‐domain OCT systems required arterial occlusion to create the blood free environment needed for image acquisition and could not reliably scan vessel diameters encountered in the peripheral circulation. However, the frequency‐domain OCT (FD‐OCT) system currently FDA approved for use in the United States does not require arterial occlusion to generate images and permits a greater scan diameter allowing for exploratory use in peripheral arteries. To our knowledge, this is the first report using non‐occlusive OCT imaging to serve as an adjunct to endovascular intervention for femoropopliteal disease. We illustrate the feasibility of acquiring high resolution images of a spiral dissection of the superficial femoral artery following balloon angioplasty that was not adequately visualized by angiography.

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.

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.

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.

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.

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

Abstract. Evidence suggests high-resolution, high-contrast, 100  frames/s 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 200-μm spacing between IVOCT image frames. Tests on a digital synthetic phantom gave a registration error of only +1.3±2.7  μm (signed distance). Visual assessment of randomly presented nearby frames suggested registration accuracy within 1 IVOCT frame interval (−25.0±174.3  μm). 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.