medwireNews: The presence of microplastics and nanoplastics (MNPs) in carotid plaques may be associated with an increased risk for myocardial infarction, stroke, or death among people with asymptomatic carotid artery disease, study findings indicate.
“Recent studies performed in preclinical models have led to the suggestion of MNPs as a new risk factor for cardiovascular diseases,” write Raffaele Marfella (University of Campania “Luigi Vanvitelli”, Naples, Italy) and co-authors in The New England Journal of Medicine.
They add: “Data from in vitro studies suggest that specific MNPs promote oxidative stress, inflammation, and apoptosis in endothelial and other vascular cells; animal models support a role for MNPs in altered heart rate, cardiac-function impairment, myocardial fibrosis, and endothelial dysfunction.”
To investigate the clinical relevance of these studies, Marfella et al assessed the presence of MNPs in excised carotid plaque specimens from 257 patients undergoing carotid endarterectomy for asymptomatic extracranial high-grade (>70%) internal carotid artery stenosis.
Analysis by pyrolysis–gas chromatography–mass spectrometry showed that more than half (58.4%) of patients had evidence of polyethylene in their carotid artery plaque, with a mean level of 21.7 μg per mg of plaque. In addition, 12.1% had measurable amounts of polyvinyl chloride, at a mean level of 5.2 μg per mm of plaque.
Furthermore, electron microscopy revealed visible, jagged-edged foreign particles, nearly all of which were smaller than 1 μm in size, among plaque macrophages and scattered in the external debris, while linear regression analysis identified a correlation between the amount of polyethylene present in the plaques and the expression levels of four pro-inflammatory markers: interleukin (IL)-18, IL-1β, IL-6, and tumor necrosis factor-α.
Marfella and colleagues report that patients with evidence of MNPs were younger than those without MNPs (median age 71 vs 73 years), more likely to be men (77.3 vs 73.8%), and less likely to have hypertension (52.0 vs 64.5%). Of note, the incidence of MNPs did not appear to differ by the geographic area where patients lived or the centers where they were enrolled.
During a mean 34 months of follow-up, 38 (14.8%) patients experienced a myocardial infarction or stroke or died from any cause.
The researchers calculated that, after adjustment for cardiovascular risk factors, the composite risk for any of these events was a significant 4.53-fold higher among the individuals who had MNPs detected within their atheroma relative to those who did not, with event rates at 20.0% and 7.5%, respectively.
Despite the strong association, Marfella et al stress that their findings “do not prove causality.”
They write: “The association between the presence of MNPs within plaque and the incidence of a composite of cardiovascular disease or death outcomes may also entail the risk from exposure to other residual, unmeasured confounding variables, such as unknown exposures during the life course of the patient or, more broadly, the health status and behaviors of the patients.”
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