Comparing thrombus aspirate pathology with OCT-verified plaque characteristics in acute coronary syndromes

Abstract Introduction OCT-pathology correlation studies have contributed to unravel basis of acute coronary syndromes (ACS), including ruptured fibrous caps (RFC), intact fibrous caps (IFC), and calcified nodules through fibrous caps (CN). However, it remains unclear whether intravascular imaging-based plaque characterization appropriately correlates with pathologic basis of occurrence of ACS. Purpose To assess whether an OCT-based diagnosis of RFC, IFC, and CN corresponds with pathological characterization of athero-thrombus aspirates in ACS patients. The study assessed short- and long-term outcomes in patients with OCT-diagnosed plaque complications. Methods The study included 160 consecutive ACS patients who underwent pre-PCI thrombus aspiration from 2016–2023, meeting the following inclusion criteria: - High thrombus burden, as per guidelines - OCT imaging quality suitable to classify RFC, IFC, and CN Pathologic characterization Samples were blindly analyzed for thrombus and plaque material (i.e. cholesterol clefts, macrophages - both foam macrophages and siderophages, - calcium, fibrous tissue). Serial sections were stained with and immunestained for pan-macrophage marker-CD68, M1 markers (i.e. CD80, CD86, IL-6) and M2 identifiers (i.e. CD163, CD206, TGF-β, IL10). Samples with plaque material were classified as RFC-derived, while thrombus-only samples were considered absence of plaque material (i.e. Non-RFC-derived). Clinical Evaluation Clinical outcomes were assessed at 100 days and 5 years. Major adverse cardiac events (MACE) included cardiac death, non-fatal ACS, ischemia-driven revascularization, cardiogenic shock, and heart failure requiring hospitalization. Results Plaque material was significantly more prevalent in RFC than in IFC samples (63% vs. 27%) (p = 0.0001). (Table 1). Immunostaining for CD68 pan-macrophages and M1 and M2 macrophage polarizations revealed the co-presence of both phenotypes in all plaque-containing samples, regardless of the OCT classification (RFC, IFC, or CN) (TABLE). The M1/M2 marker ratio was 5:1. Short-term MACE (100 days) was significantly higher in the 97 patients with OCT-RFC-ACS (30.9%) than in the 60 patients with OCT-IFC-ACS (15.0%, P=0.028). However, long-term MACE rates (median follow-up: 5.0 years) were comparable between OCT-RFC-ACS (33.7%) and OCT-IFC-ACS (40.5%, P=0.66). Conclusions Our pathology-OCT study showed plaque material is more prevalent in OCT-RFC than OCT-IFC but not exclusive. The presence of plaque material in 27% of OCT-IFC samples suggests OCT may underestimate RFC (sensitivity vs. pathology = 79%); in addition, although M1 macrophages predominate, they are not exclusive. Given that long-term follow-up suggests similar outcomes between OCT RFC-ACS and IFC-ACS patients, more information is needed to understand impact of OCT-based diagnosis of plaque complications in ACS patients.OCT and PATHOLOGY DIAGNOSIS Cumulative Incidence of MACE