Coronary CT angiography-derived pericoronary fat attenuation index: Post-mortem histopathological correlation in fatal plaques

Objectives: The fat attenuation index (FAI) is a biomarker that has recently gained attention for reflecting perivascular inflammation in coronary arteries. We investigated the utility of the FAI in identifying high-risk coronary plaques responsible for sudden cardiac death (SCD). Methods: Using multiphase post-mortem CT angiography (MPMCTA), we analyzed culprit plaques from 35 individuals who died from acute coronary syndrome, comparing these to control vessels from within-subject unaffected coronary arteries, with FAI measurement. Histopathological examination of culprit plaques assessed intraplaque inflammation, adventitial inflammation, and vasa vasorum density. Results: Perivascular FAI values were significantly higher in culprit lesions than control lesions, -62.5 ± 10.4 vs. -68.5 ± 7.2 HU, respectively (p = 0.003). However, no significant differences in FAI were found between culprit lesions with and without local histopathological inflammation (p = 0.378). Additionally, FAI values = -70.1 HU were more common in culprit than control lesions, though this threshold did not reach statistical significance (p = 0.081). Other imaging biomarkers, including the napkin-ring sign (p = 0.049) and plaque enhancement (p = 0.024), were more closely associated with histopathological inflammation. Conclusion: Our findings support FAI as a surrogate marker of high-risk coronary artery disease, although more extensive studies are needed to confirm its predictive accuracy for SCD. Integrating FAI with routine coronary CT angiography features could improve risk stratification in clinical settings.