The Use of Intracoronary Optical Coherence Tomography in Interventional Cardiology: Safety, Feasibility and Clinical Applications

Interventional cardiology has witnessed tremendous change since 1977 when Andreas Gruentzig successfully performed the first balloon angioplasty. Whereas initial concerns revolved around maintaining vessel patency with issues of recoil and restenosis, the introduction of stents changed the landscape forever. Inherent with their use, stents, and, more specifically, drugeluting stents (DES), have become central to improved patient outcomes but, at some cost. Catastrophic, yet fortunately still rare complications such as stent thrombosis have re-ignited an intense need for greater scrutiny when developing and, subsequently implanting DES into our patients. The demand for detailed information regarding coronary artery disease has seen intravascular imaging become pivotal at delineating atherosclerosis and tissue responses following stent implantation. In fact, the strategy that relied on angiography alone is evolving to include better confirmation of disease severity and stenting technique. With this, optical coherence tomography (OCT) has grown exponentially with a broad diffusion amongst catheterisation laboratories worldwide. Optical coherence tomography is a procedurally demanding technique. Individual experience is often frustrated initially with disappointing images as a result of inadequate blood clearance. With perseverance and adequate proctorship however, one cannot help but be impressed by the clarity and resolution afforded by this imaging modality. It is these images that have attracted considerable attention at cardiology conferences internationally and have helped instil OCT as the most sensitive intravascular imaging technique available today. The aim of this thesis was to evaluate the role of OCT in contemporary coronary intervention. Part 1 embraces the principles of the technique and the physical properties of OCT (chapter 2) and gives an insight into where OCT is placed compared to other intravascular imaging modalities (chapter 3). Despite the adoption of OCT in more and more catheterisation laboratories, little has been documented as to its safety, so, in chapter 4, we review the procedural safety of intracoronary OCT in a large group of patients across six leading European centres

Type 2 MI and Myocardial Injury in the Era of High-sensitivity Troponin

Troponin has been the cornerstone of the definition of MI since its introduction to clinical practice. High-sensitivity troponin has allowed clinicians to detect degrees of myocardial damage at orders of magnitude smaller than previously and is challenging the definitions of MI, with implications for patient management and prognosis. Detection and diagnosis are no doubt enhanced by the greater sensitivity afforded by these markers, but perhaps at the expense of specificity and clarity. This review focuses on the definitions, pathophysiology, prognosis, prevention and management of type 2 MI and myocardial injury. The five types of MI were first defined in 2007 and were recently updated in 2018 in the fourth universal definition of MI. The authors explore how this pathophysiological classification is used in clinical practice, and discuss some of the unanswered questions in this era of availability of high-sensitivity troponin

Physiological predictors of acute coronary syndromes: emerging insights from the plaque to the vulnerable patient

In this review, the authors explore the evolving evidence linking physiological assessment of coronary artery disease with plaque progression and vulnerability. Reducing adverse clinical events remains the ultimate goal for diagnostic tests, and this review highlights evidence supporting the prognostic value of physiological metrics in predicting outcomes. Historical and contemporary studies support synergy among lesion severity, ischemia, plaque vulnerability, and patient prognosis. Ischemia contributes to clinical events through association with plaque burden, but this review addresses the emerging concept that it associates with atherothrombosis via disturbed lesion hemodynamics. Biomechanical pathophysiological forces including endothelial shear stress-the frictional force generated by blood flow on the vessel wall-are increasingly linked with atherogenesis, vulnerable plaque morphology, and platelet and leukocyte activation. The authors conclude by transitioning from the model of the vulnerable plaque to the concept of the "vulnerable patient," looking more broadly at physiological contributors to Virchow's triad underpinning acute coronary syndrome

An optical coherence tomography study of a biodegradable vs. durable polymer-coated limus-eluting stent: a LEADERS trial sub-study

Aims Incomplete endothelialization has been found to be associated with late stent thrombosis, a rare but devastating phenomenon, more frequent after drug-eluting stent implantation. Optical coherence tomography (OCT) has 10 times greater resolution than intravascular ultrasound and thus appears to be a valuable modality for the assessment of stent strut coverage. The LEADERS trial was a multi-centre, randomized comparison of a biolimus-eluting stent (BES) with biodegradable polymer with a sirolimus-eluting stent (SES) using a durable polymer. This study sought to evaluate tissue coverage and apposition of stents using OCT in a group of patients from the randomized LEADERS trial. Methods and results Fifty-six consecutive patients underwent OCT during angiographic follow-up at 9 months. OCT images were acquired using a non-occlusive technique at a pullback speed of 3 mm/s. Data were analysed using a Bayesian hierarchical random-effects model, which accounted for the correlation of lesion characteristics within patients and implicitly assigned analytical weights to each lesion depending on the number of struts observed per lesion. Primary outcome was the difference in percentage of uncovered struts between BESs and SESs. Twenty patients were included in the analysis in the BES group (29 lesions with 4592 struts) and 26 patients in the SES group (35 lesions with 6476 struts). A total of 83 struts were uncovered in the BES group and 407 out of 6476 struts were uncovered in the SES group [weighted difference −1.4%, 95% confidence interval (CI) −3.7 to 0.0, P = 0.04]. Results were similar after adjustment for pre-procedure lesion length, reference vessel diameter, number of implanted study stents, and presence of stent overlap. There were three lesions in the BES group and 15 lesions in the SES group that had ≥5% of all struts uncovered (difference −33.1%, 95% CI −61.7 to −10.3, P < 0.01). Conclusion Strut coverage at an average follow-up of 9 months appears to be more complete in patients allocated to BESs when compared with SESs. The impact of this difference on clinical outcome and, in particular, on the risk of late stent thrombosis is yet to be determine

Five-year follow-up of underexpanded and overexpanded bioresorbable scaffolds: Self-correction and impact on shear stress

Underexpansion and overexpansion have been incriminated as causative factors of adverse cardiac events. However, dynamic biological interaction between vessel wall and scaffold may attenuate the adverse haemodynamic impact of overexpansion or underexpansion

An optical coherence tomography and endothelial shear stress study of a novel bioresorbable bypass graft

Endothelial shear stress (ESS) plays a key role in the clinical outcomes in native and stented segments; however, their implications in bypass grafts and especially in a synthetic biorestorative coronary artery bypass graft are yet unclear. This report aims to examine the interplay between ESS and the morphological alterations of a biorestorative coronary bypass graft in an animal model. Computational fluid dynamics (CFD) simulation derived from the fusion of angiography and optical coherence tomography (OCT) imaging was used to reconstruct data on the luminal anatomy of a bioresorbable coronary bypass graft with an endoluminal "flap" identified during OCT acquisition. The "flap" compromised the smooth lumen surface and considerably disturbed the local flow, leading to abnormally low ESS and high oscillatory shear stress (OSI) in the vicinity of the "flap". In the presence of the catheter, the flow is more stable (median OSI 0.02384 versus 0.02635, p < 0.0001; maximum OSI 0.4612 versus 0.4837). Conversely, OSI increased as the catheter was withdrawn which can potentially cause back-and-forth motions of the "flap", triggering tissue fatigue failure. CFD analysis in this report provided sophisticated physiological information that complements the anatomic assessment from imaging enabling a complete understanding of biorestorative graft pathophysiology

Association of sex with outcomes in patients undergoing percutaneous coronary intervention: a subgroup analysis of the global leaders randomized clinical trial

Importance: Women experience worse ischemic and bleeding outcomes after percutaneous coronary intervention (PCI). Objectives: To assess the association of sex with patient outcomes at 2 years after contemporary PCI and with the efficacy and safety of 2 antiplatelet strategies. Design, Setting, and Analysis: This study is a prespecified subgroup analysis of the investigator-initiated, prospective, randomized GLOBAL LEADERS study evaluating 2 strategies of antiplatelet therapy after PCI in an unselected population including 130 secondary/tertiary care hospitals in different countries. The main study enrolled 15 991 unselected patients undergoing PCI between July 2013 and November 2015. Patients had an outpatient clinic visit at 30 days and 3, 6, 12, 18, and 24 months after the index procedure. Data were analyzed between January 1, 2019, and March 31, 2019. Interventions: Eligible patients were randomized to either the experimental or reference antiplatelet strategy. Experimental strategy consisted of 1 month of dual antiplatelet therapy (DAPT) followed by 23 months of ticagrelor monotherapy, while the reference strategy comprised of 12 months of DAPT followed by 12 months of aspirin monotherapy. Main Outcomes and Measures: The primary efficacy end point was the composite of all-cause mortality and new Q-wave myocardial infarction at 2 years. The secondary safety end point was Bleeding Academic Research Consortium type 3 or 5 bleeding. Results: Of the 15 968 patients included in this study, 3714 (23.3%) were women. The risk of the primary end point at 2 years was similar between women and men (adjusted hazard ratio [HR], 1.00; 95% CI, 0.83-1.20). Compared with men, women had higher risk of Bleeding Academic Research Consortium type 3 or 5 bleeding (adjusted HR, 1.32; 95% CI, 1.04-1.67) and hemorrhagic stroke at 2 years (adjusted HR, 4.76; 95% CI, 1.92-11.81). At 2 years, there was no between-sex difference in the efficacy and safety of the 2 antiplatelet strategies. At 1 year, compared with DAPT, ticagrelor monotherapy was associated with a lower risk of bleeding in men (HR, 0.72; 95% CI, 0.53-0.98) but not in women (HR, 1.23; 95% CI, 0.80-1.89; P for interaction = .045). Conclusions and Relevance: Compared with men, women experienced a higher risk of bleeding and hemorrhagic stroke after PCI. The effect of 2 antiplatelet strategies on death and Q-wave myocardial infarction following PCI did not differ between the sexes at 2 years. Trial Registration: ClinicalTrials.gov identifier: NCT01813435

Scaling climate services for agriculture in the Global South: an assessment of practitioners’ needs

Several CS projects have been implemented recently to meet the increasing demand from farmers and other decision makers in the Global South for climate information and agro-advisories. This has led to two main concerns: (1) how CS products and services can be improved for the benefit of small-scale farmers at different scales; and (2) how to sustain (successful) CS projects beyond the end their lifetime. Addressing these two questions will require pathways for scaling CS projects. Hence, 20 CS projects across Asia, Africa and Latin America were reviewed through a mix of desk research and interviews (both virtual and face-to-face) with project practitioners to solicit their views of and experiences with CS projects, the provided services and products, and scaling. Results showed that the CS sector has clearly matured in recent decades. CS providers focus mainly on translation and transfer of climate date, and rely on observational data and climate and hydrological models, from national, international and private sources. There is great diversity of products in terms of format, content, way of communication, frequency, and target groups, which shows the potential to tailor CS products and their messages to the specific needs of end-users and diverse contexts. The design and implementation of CS depends on a myriad of actors working together along the CS value chain. For historical reasons many of the selected projects in the South were coordinated and/or funded by NGOs, but increasingly government agencies and/or private sector have become active partners as well. Despite these positive developments, one of the main challenges of scaling CS comes from the collaboration between different institutions. Whereas different organizations may agree on the common goals, they often do not on the way of working. Overall through the future for CS looks positive, but there are some additional concerns related to access to information, the reliability of data and the confidence people have in the services, the human resources and additional funding required for scaling CS, and the risk that small-scale farmers, and in particular the poor, women and ethnic minorities, are left out. Several recommendations are made to ensure the benefit of CS for small-scale farmers through scaling