Relationship between plaque burden and plaque vulnerability in patients with acute coronary syndromes versus chronic coronary syndrome

Abstract Background The relationship between plaque burden and plaque vulnerability based on clinical presentations has not been fully investigated. Objective The aim of this study was to compare the relationship between plaque burden and plaque vulnerability in patients with acute coronary syndromes (ACS) versus chronic coronary syndrome (CCS). Methods This is an observational, single-center cohort study. Patients who underwent both coronary computed tomography angiography (CTA) and optical coherence tomography (OCT) before coronary intervention were enrolled. All OCT and CTA images were analyzed at the core laboratory. All plaques were detected in culprit vessels using CTA, and total plaque volume (TPV) and OCT features were assessed at the corresponding sites. A layered plaque was defined as a plaque with one or more layers of different optical densities and a clear demarcation from underlying components. The layer arc was measured at 1-mm intervals. The layer index, which is equivalent to layer volume, was defined as mean layer arc × layer length. All plaques were divided into three groups according to the tertile range of TPV (low TPV: <96.5 mm3, moderate TPV: 96.5 – 164.7 mm3, high TPV: ≥164.8 mm3). The effect modification of clinical presentations (CCS or ACS) on the association between TPV and OCT features was investigated. Results A total of 990 plaques were imaged by OCT in 419 patients: 445 plaques in 190 (45.3%) patients who presented with ACS and 545 in 229 (54.7%) with CCS. The prevalence of thin-cap fibroatheroma (TCFA) was higher as plaque volume increased in both groups (low vs. moderate vs. high TPV group: 18.4% vs. 37.8% vs. 52.3% in ACS; 16.2% vs. 19.9% vs. 30.6% in CCS; interaction P=0.066). However, the effect modification of clinical presentations on the associations of TPV with macrophage, lipid arc, and layer index was statistically significant. Macrophage was more prevalent in plaques with greater TPV in patients who presented with ACS but not in those who presented with CCS (low vs. moderate vs. high TPV group: macrophage 57.4% vs. 71.8% vs. 82.4% in ACS; 63.4% vs. 67.8% vs. 66.7% in CCS; interaction P=0.004). Lipid arc was more strongly associated with TPV in patients who presented with ACS than in those with CCS (low vs. moderate vs. high TPV group: 116 [76-157] vs. 166 [115-210] vs. 175 [140-221] in ACS; 118 [80-154] vs. 143 [102-187] vs. 150 [102-199] in CCS; interaction P=0.028). Conversely, layer index was more weakly associated with TPV in patients who presented with ACS than in those who presented with CCS (low vs. moderate vs. high TPV group: 0 [0-0] vs. 0 [0-365] vs. 0 [0-903] in ACS; 0 [0-756] vs. 235 [0-1266] vs. 552 [0-1704] in CCS; interaction P=0.046) (Figure 1). Conclusions Greater plaque burden was closely related to the level of plaque vulnerability in ACS, whereas this relationship was less obvious in CCS.Figure 1