Mixed spotty calcification identifies a coronary plaque phenotype associated with heightened metabolic activity distinct from calcific disease

Background

Spotty calcification is associated with high-risk coronary plaque, but the biological mechanisms underlying different plaque morphologies remain poorly defined. Current paradigms focus on plaque burden rather than biological activity.

Purpose

To determine whether coronary plaque morphology and size define distinct metabolic phenotypes and identify biologically active plaque subtypes.

Methods

In 835 participants from the BioHEART-CT cohort, we analysed 1,634 coronary plaques on CT coronary angiography, classified by size (≤1 mm, 1–3 mm, 3–5 mm) and morphology (calcified vs mixed). Spotty calcification was defined as lesions measuring 1–3 mm or 3–5 mm. Targeted plasma metabolomics (53 metabolites) was performed using LC–MS. Associations between metabolite profiles and plaque subtypes were assessed using multivariable Poisson regression, adjusted for clinical risk factors. Metabolite set enrichment analysis identified key biological pathways.

Results

Plaque metabolic activity was highly dependent on morphology and size. Mixed spotty calcifications (1–3 mm) demonstrated the greatest metabolic dysregulation, with 16 of 53 metabolites significantly associated with plaque burden, whereas small plaques (≤1 mm) showed no metabolic activity. Calcified plaques exhibited minimal metabolic associations, indicating biological quiescence. The metabolic signature of mixed spotty calcification was characterised by disruption of glycine, serine, and threonine metabolism (FDR=0.0275), alongside alterations in amino acid and phospholipid pathways, consistent with inflammatory and bioenergetic stress. Several metabolites (including cysteamine, phosphocholine, and thiamine) were inversely associated with plaque burden, while uridine and 2-arachidonylglycerol were associated with a plaque-free phenotype. Metabolic activity did not correlate with plaque size or calcium burden but was specific to mixed morphology, indicating that vulnerability is driven by plaque composition rather than disease extent.

Conclusion

Mixed, spotty calcification defines a metabolically active, biologically distinct coronary plaque phenotype, whereas calcified plaques are relatively inactive. These findings challenge burden-based models of atherosclerosis and support a shift towards morphology- and biology-driven risk stratification, with potential implications for early identification of vulnerable patients and targeted prevention strategies.

Table 1 – Results of Poisson regression analysis showing the association between metabolite expression and coronary artery plaque characteristics.