OR8-3 | Evaluation of the Changes in Fibrous Cap Thickness in Nonculprit Coronary Artery Plaques Using Serial OCT Imaging and Serum Biomarkers

There is limited experience using optical coherence tomography (OCT) to characterize factors associated with temporal changes in fibrous cap (FC) thickness that may result in high-risk plaque precursors such as thin-cap fibroatheromas. Using a novel, automated volumetric FC measurement tool Baseline (B) and Follow-up (F) OCT imaging at 12 months were co-registered and manually analyzed for plaque features (mean/max lipid arc) before undergoing computational volumetric assessment of the fibrous cap (FC). FC changes were described using F minus B minimum thickness, such that larger change scores indicate thicker FC at F. Conversely, larger values of the change (F minus B) in the fibrous area index (<100 and <200mm2) represent greater areas of thin FC at F. Pearson's correlation coefficient was calculated for each change in FC measurement with biomarkers and baseline OCT parameters. 46 participants (mean age 63±9) underwent both B and F evaluations. Higher levels of the biomarker MMP-9 were associated with thinner FC minimums at F (r=-0.33, p=0.03), but not with the overall % of thin FC area via the FC area index (p>0.05). Higher values of the baseline mean and max lipid arc were associated with larger areas of thin FC as measured by FC area indices (p<0.001). A novel, automated volumetric FC measurement tool confirmed the association between increased levels of MMP-9 and minimal FC thickness over time. Elevated MMP-9 expression has been linked to inflammation and extracellular matrix degradation. This finding provides insight into a potential pathophysiologic correlation contributing to temporal changes in FC thickness.