Relationship between coronary artery calcium score and plaque vulnerability by coronary CT angiography in non-obstructive coronary artery disease

Abstract Background Coronary artery calcium score (CACS) is recommended to improve risk-stratification in patients with chronic coronary syndrome by identifying individuals with a high plaque burden and increased risk of future major adverse coronary events. Whether CACS also identifies patients with non-obstructive CAD with a vulnerable plaque phenotype at increased cardiovascular risk, is still unclear. Purpose The aim of this study was therefore to assess the relationship between CACS and compositional plaque burden in patients with non-obstructive CAD. Method We identified 1189 patients (48% women) from the Norwegian Registry of Invasive Cardiology diagnosed with chronic non-obstructive CAD by coronary computed tomography angiography (CCTA). CACS by the Agatston method and compositional coronary plaque phenotyping by CCTA were performed in all study participants. A vulnerable plaque phenotype was defined as a high burden of low-attenuating plaque. The relationship between CACS and plaque phenotype was assessed in groups of patients with high CACS >100 or low CACS ≤100. Results The median (IQR) CACS in the study population was 40(7-122). In general, patients with a high CACS (n=345, 29%) were older than those with a low CACS, and had a higher prevalence of hypertension, diabetes and statin treatment (all p<0.05), while there was no difference in prevalence of high CACS between women and men. A higher total plaque burden and higher proportions of calcified plaques were observed in patients with a high CACS, while patients with a low CACS had higher proportions of fibrous and vulnerable low-attenuation plaques (all p<0.05, Fig. 1). In multiple linear regression analysis, high CACS remained negatively associated with a higher proportion of vulnerable low-attenuation plaques after adjusting for age, sex, statin treatment and cardiovascular risk factors (β=-2.4 with 95% CI [-4.2 to -0.7], p=0.006). Conclusions In patients with chronic non-obstructive CAD, a high CACS was associated with a lower proportion of vulnerable low-attenuation plaques compared to patients with a low CACS. Following our results, a high CACS in patients with non-obstructive CAD may fail in identifying patients with a high vulnerable plaque burden. The role of CACS in risk stratification among patients with non-obstructive CAD needs further evaluation in prospective studies. Fig. 1. Total and compositional plaque burden by high or low CACSFig. 1.