Predictive value of the perivascular fat attenuation index for MACE in young people suspected of CAD

Objective The perivascular fat attenuation index (FAI) evaluated by coronary computed tomographic angiography (CCTA) has been reported to have strong prognostic value, but few studies have focused on young people. This study aimed to assess the predictive value of the perivascular FAI in young people suspected of having coronary atherosclerotic disease (CAD). Method A retrospective analysis was performed on adults aged <= 45 years who underwent CCTA due to suspected CAD between 2015 and 2016 and who were followed up for at least 5 years following their visit (n = 503). The perivascular FAI at the proximal segment of the right coronary artery (RCA) was measured and grouped into high FAI and low FAI according to the optimal cut-off value, and the association between a high FAI and major adverse cardiac events (MACE) was evaluated by Cox hazard regression. K-M survival analysis was conducted to assess the prognostic value of the perivascular FAI and improvement over traditional risk factor prediction methods. Results The event-free survival of patients in the high FAI group (FAI >=-75.2 HU) was significantly lower than that of patients in the low FAI group (FAI<-75.2 HU) at a median follow-up of 72.7 months (93.9% vs. 99.7%, P < 0.001). A high FAI (HR = 19.257, 95% CI: 2.504-148.107, P = 0.004) showed a significant correlation with an increased risk of MACE in young people. The prediction accuracy of MACE can be improved by including a high FAI on the basis of the traditional risk factor model, and the area under the curve (AUC) increased from 0.728 to 0.845 (P < 0.001). Moreover, the new model revealed significant improvements in integrated discrimination (IDI = 0.033, 95% CI: 0.009-0.103, P = 0.014) and the net reclassification index (NRI = 0.597, 95% CI: 0.000-0.699, P = 0.024). Conclusion The high perivascular FAI at the proximal segment of the RCA is significantly associated with an increased risk of long-term MACE and may be a potential tool for cardiovascular risk stratification in young people suspected of CAD.