Weekly Journal Scan: Plastic particles in carotid plaques—inactive debris or predictors of cardiovascular events?

Key points• This prospective, multicentre, observational study explored whether microplastics and nanoplastics (MNPs) are detectable within atherosclerotic plaques and whether the burden of MNPs is associated with cardiovascular disease (CVD) outcomes, as suggested by preclinical studies. 1 • The authors enrolled consecutive patients with asymptomatic carotid artery stenosis for whom carotid endarterectomy was indicated. 2The excised carotid plaque specimens were analysed for the presence of 11 different MNPs with the use of pyrolysis-gas chromatography-mass spectrometry (a quantitative technique that measures MNPs in combination), stable isotope analysis, and electron microscopy.Inflammatory biomarkers were assessed in plaque samples with enzyme-linked immunosorbent assay and immunohistochemical assay.• The primary endpoint was a composite of myocardial infarction, stroke, or death from any cause, comparing patients who had evidence of MNPs in the plaque with those without plaque MNPs.Secondary endpoints included tissue levels of the following biomarkers: interleukin (IL)-18, IL-1β, tumour necrosis factor-α (TNF-α), IL-6, CD68, CD3, and collagen.• A total of 304 patients were enrolled in the study, and 257 patients completed a mean (±standard deviation) follow-up of 34 ± 7 months.Polyethylene was detected in carotid plaques of 150 patients (58%), with a mean level of 21.7 ± 24.5 μg per milligram of plaque; 31 patients (12%) also had a measurable amount of polyvinyl chloride, with a mean level of 5.2 ± 2.4 μg per milligram of plaque.In 10 randomly selected patients, electron microscopy revealed visible, jagged-edged foreign particles within plaque macrophages and scattered as external debris.Radiographic examination showed that some of these particles included chlorine.• At 34 months of follow-up, a primary endpoint event occurred in 8 of 107 patients (7.5%) who did not have evidence of plaque MNPs (2.2 events per 100 patient-years) and in 30 of 150 patients (20.0%) who had evidence of plaque MNPs (6.1 events per 100 patient-years; hazard ratio 4.53; 95% confidence interval 2.00-10.27;P < .001by Cox regression analysis with adjustment for CVD risk factors).Linear regression analysis revealed a direct correlation between the amount of polyethylene present in plaque samples and levels of IL-18, IL-1β, IL-6, TNF-α, CD3, and CD68 (markers of lymphocyte and macrophage infiltration, respectively) and an inverse correlation with collagen content.