Abstract Body: Introduction
Non-invasive cardiac imaging for assessing cardiovascular risk is challenging in obese patients. Intrathoracic adipose tissue, encompassing mediastinal adipose tissue (MAT) and pericardial adipose tissue (PAT), has emerged as a promising marker for cardiovascular risk. However, standard measurement methods for MAT and PAT and their diagnostic utility in the severe obese population remain unknown.

Methods
We retrospectively analyzed the stress cardiovascular magnetic resonance (CMR) imaging of 790 consecutive patients between 2018-2021, including 199 with severe obesity (BMI ≧ 40 kg/m²). Using the scout images (HASTE sequence), PAT and MAT were assessed as linear thickness of adipose on single axial slices. PAT was measured at the anterior mid right ventricle between the myocardium and parietal pericardium. MAT was measured at two levels: between the sternum and 1) pulmonary artery bifurcation and 2) aortic arch, respectively. Multivariable competing risk survival analysis was performed for the composite outcome of cardiac death or cardiac hospitalizations, adjusted for BMI, traditional cardiac risk factors, the presence of late gadolinium enhancement (LGE) and inducible ischemia.

Results
Survival analysis showed PAT, but not MAT, was a significant predictor of adverse cardiac events for all subjects across a BMI range of 13.4-66.7 kg/m² with a sub-hazard ratio (SHR) of 1.087, along with LGE and inducible ischemia (Table 1). Among the severe obese group (BMI ≧ 40 kg/m²), PAT, LGE and inducible ischemia remain significant predictors for cardiac events with similar SHR. BMI or the traditional cardiac risk factors were not significant predictors in either the full cohort or the severe obesity.

Conclusions
PAT predicts adverse cardiac outcomes across BMI strata, including severe obesity, and can be readily attained from CMR by simple linear measurements.