Relationship between coronary artery calcium score and plaque vulnerability in patients with established coronary artery disease

Abstract Introduction Coronary artery calcium (CAC) score is widely used for risk stratification. However, in patients with established coronary artery disease (CAD), its clinical implication and relationship with plaque vulnerability have not been fully investigated. Purpose We sought to investigate the relationship between CAC score and plaque vulnerability assessed by optical coherence tomography (OCT). Methods Patients with CAD who had both CAC score and OCT prior to percutaneous coronary intervention were included. The patients with a prior history of coronary revascularization were excluded. Patients were divided into five groups based on CAC score; CAC score of 0, 1-99, 100-399, 400-999, and over 1000. Vulnerable features in culprit plaque assessed by OCT were compared among these five groups. Results In 460 patients, the prevalence of lipid-rich plaque, macrophage, and cholesterol crystal significantly differed among the five groups: lowest in the patients with a CAC score of zero. The prevalence of thin-cap fibroatheroma (TCFA) tended to be lower in those with a CAC score of zero (Figure). In the two-group comparison between the group with a CAC score of zero and the other four groups, the prevalence of lipid-rich plaque (60.5 vs. 85.9%, p < 0.001), macrophage (48.8 vs. 74.1%, p < 0.001), TCFA (16.3 vs. 35.0%, p = 0.013), and cholesterol crystal (11.6 vs. 32.9%, p = 0.004) was significantly lower in the patients with CAC score of zero. No significant difference in vulnerable features was observed among the four groups with CAC scores > 0. CAC score of zero was independently negatively associated with the lipid-rich plaque (odds ratio [OR] 0.246, p < 0.001), macrophage (OR 0.348, p = 0.003), TCFA (OR 0.285, p = 0.006), and cholesterol crystal (OR 0.273, p = 0.010) after adjustment with patient characteristics. Conclusion This is the first study that investigated the relationship between CAC score and plaque vulnerability assessed by OCT in patients with known CAD. Patients with CAC score of zero have a significantly lower prevalence of vulnerable plaque features compared to those with CAC score > 0.