Mechanisms of stent thrombosis: insights from optical coherence tomography

Artificial Intelligence for the Interventional Cardiologist: Powering and Enabling OCT Image Interpretation

Intravascular optical coherence tomography (IVOCT) is a form of intra-coronary imaging that uses near-infrared light to generate high-resolution, cross-sectional, and 3D volumetric images of the vessel. Given its high spatial resolution, IVOCT is well-placed to characterise coronary plaques and aid with decision-making during percutaneous coronary intervention. IVOCT requires significant interpretation skills, which themselves require extensive education and training for effective utilisation, and this would appear to be the biggest barrier to its widespread adoption. Various artificial intelligence-based tools have been utilised in the most contemporary clinical IVOCT systems to facilitate better human interaction, interpretation and decision-making. The purpose of this article is to review the existing and future technological developments in IVOCT and demonstrate how they could aid the operator.

Factors Impacting Stent Thrombosis in Patients With Percutaneous Coronary Intervention and Coronary Stenting: A Systematic Review and Meta-Analysis

Stent thrombosis (ST) is a frequently reported complication in cardiac patients with percutaneous coronary intervention (PCI) that adversely impacts their prognostic outcomes. Medical literature reveals several baseline characteristics of PCI patients that may predict their predisposition to ST and its potential complications. Our systematic review and meta-analysis aimed to determine the diagnostic significance of these baseline parameters in terms of determining the risk of ST among adult patients with PCI. 

We statistically evaluated 18 baseline characteristics of more than 15,500 PCI patients to delineate their stent thrombosis attribution. We included a number of articles focusing on baseline parameters in-stent thrombosis-related PCI scenarios. We explored the articles of interest based on inclusion/exclusion parameters across PubMed, JSTOR, Cochrane library, Google Scholar, and Embase. Medical subject headings (MeSH) words included “stent thrombosis,” “percutaneous coronary intervention,” and “coronary stenting.” We extracted the research articles published between 2005 and 2021 on April 20, 2021. The included studies also focused on procedures and clinical factors concerning their association with PCI-related ST.

Our findings ruled out the progression of abnormal left ventricular ejection fraction (LVEF)-related stent thrombosis in PCI patients (odds ratio {OR}: 9.68, 95% CI: 1.88-49.90, p=0.007). We found an insignificant clinical correlation between stent thrombosis and PCI in the setting of acute coronary syndrome (ACS). Our study outcomes further revealed the absence of stent thrombosis in PCI patients with antiplatelet prescription (OR: 32.42, 95% CI: 21.28-49.39). The findings affirmed the absence of ST in PCI patients receiving aspirin therapy (OR: 32.77, 95% CI: 18.73-57.34; OR: 4.59, 95% CI: 1.97-10.73). The majority of the included studies negated the clinical correlation of stent thrombosis with diabetes mellitus in the setting of PCI (OR: 0.49, 95% CI: 0.06-3.78). Our study did not reveal statistically significant results based on stent thrombosis in PCI patients with drug-eluting stents (OR: 2.91, 95% CI: 0.35-24.49). The findings also did not reveal the impact of cardiac biomarker elevation on stent thrombosis in PCI patients (OR: 8.42, 95% CI: 2.54-27.98, p=0.0005). Eight studies revealed a statistically insignificant correlation between myocardial infarction and stent thrombosis in PCI scenarios (OR: 2.69, 95% CI: 0.89-8.11, p=0.08). The clinical correlation between PCI and stent thrombosis/major bleeding in the setting of hypertension also proved statistically insignificant at 0.67 (OR: 1.31, 95% CI: 0.38-4.51, p=0.97). The study findings did not correlate mean body mass index and multivessel coronary artery disease with ST in PCI scenarios (OR: 1.98, 95% CI: 0.02-239.58, p=0.78; OR: 1.09, 95% CI: 0.58-2.04, p=0.80). Only two studies revealed statistically significant results confirming stent thrombosis in PCI patients with a prior history of PCI (OR: 0.49, 95% CI: 0.23-1.06; OR: 0.33, 95% CI: 0.02-5.59; p=0.03).

Our findings question the clinical significance of baseline characteristics in terms of predicting stent thrombosis in PCI patients. The results support the requirement of future studies to investigate complex interactions between procedural, medicinal, genetic, and patient-related factors contributing to the development of stent thrombosis in PCI patients. 

Relationship between atherogenic index of plasma and stent thrombosis in patients with acute coronary syndrome

OBJECTIVE

Stent thrombosis (ST) is an uncommon but serious complication in patients undergoing percutaneous coronary intervention (PCI). This study aimed to investigate the effect of atherogenic index of plasma (AIP) on ST.

METHODS

Among the 10,258 patients who underwent coronary angiography between January 2018 and December 2020, 239 patients who underwent PCI with the diagnosis of acute coronary syndrome (ACS) due to ST were included as the study group (ST group) and 459 patients who underwent percutaneous intervention for ACS and did not have any in-stent lesion as the control group (non-ST group). ST classification was done according to the Academic Research Consortium definition.

RESULTS

The mean age of the patients was 63.3±10.6 years (483 male, 69.2%). The groups were similar in terms of characteristic properties, comorbidities, and the drugs being used (p>0.05 for all). Drug eluting stents were used in 86.5% of the patients. In the ST group, the median time from stent implantation to thrombosis was 285 days. Mean AIP and the ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) were statistically significantly higher in the ST group than in the controls (p<0.001 and p=0.018, respectively), and a positive correlation was observed between time from stent implantation to thrombosis and AIP and TG/HDL-C (rS=0.229, p=0.010 and rS=0.222, p=0.010, respectively). Multivariate logistic regression analysis revealed that stent length, prior ST elevation myocardial infarction, TG/HDL-C, and AIP were independent predictors of ST.

CONCLUSION

AIP is an easy calculable biomarker, and the performance of AIP to predict ST is better than TG/HDL-C.

Thrombotic responses to coronary stents, bioresorbable scaffolds and the Kounis hypersensitivity-associated acute thrombotic syndrome

Percutaneous transluminal coronary angioplasty with coronary stent implantation is a life-saving medical procedure that has become, nowadays, the most frequent performed therapeutic procedure in medicine. Plain balloon angioplasty, bare metal stents, first and second generation drug-eluting stents, bioresorbable and bioabsorbable scaffolds have offered diachronically a great advance against coronary artery disease and have enriched our medical armamentarium. Stented areas constitute vulnerable sites for endothelial damage, endothelial dysfunction, flow turbulence, hemorheologic changes, platelet dysfunction, coagulation changes and fibrinolytic disturbances. Implant surface attracts several proteins such as albumin, fibronectin, fibrinogen, and complement that lead to complement system activation. Macrophages recognize the implant as foreign substance due to protein adsorption and its continuous presence results in macrophage differentiation and fusion into foreign body giant cells. Polymer coating, stent metallic platforms and the released drugs can act as strong antigenic complex that apply continuous, repetitive, persistent and chronic hypersensitivity irritation to the coronary intima. The concomitant administration of oral antiplatelet drugs and environmental exposures can induce hypersensitivity inflammation. A class of platelets, activated via high-affinity and low-affinity IgE hypersensitivity receptors FCγRI, FCγRII, FCεRI and FCεRII, can induce Kounis hypersensitivity-associated thrombotic syndrome inside the stented coronaries. Type III variant of this syndrome is diagnosed when coronary artery stent thrombosis is associated with thrombus infiltrated by eosinophils or mast cells and/or when coronary intima, media and adventitia adjacent to stent, is infiltrated by eosinophils or mast cells. Careful history of hypersensitivity reactions to all implanted materials and concomitant drugs with monitoring of inflammatory mediators as well as lymphocyte transformation studies to detect hypersensitivity must be undertaken in order to avoid disastrous consequences. Food and Drug Administration recommendations for coronary stent implantation should be applied also to bioresorbable scaffolds. Further studies with inert and non-allergenic implants are necessary.