Transcriptome analysis from human epicardial adipose tissue biopsies analyzed according to postoperative atrial fibrillation occurrence after cardiac surgery

Introduction: Post-operative atrial fibrillation (POAF) is a frequent complication after cardiac surgery, but its pathophysiology remains incompletely understood. Considering that epicardial adipose tissue (EAT) is in close vicinity with the atrial myocardium, we hypothesized that a specific pre-operative EAT phenotype would be associated to POAF onset following surgery. Methods: Patients undergoing cardiac surgery prospectively enrolled in the POMI-AF cohort between February 2016 and June 2017 were studied. EAT samples were collected at the beginning of surgery. Whole-tissue gene expression patterns and the stromal and vascular fraction (SVF) cellular composition were explored. Patients were followed after surgery by continuous ECG to detect POAF onset. Results: Among the 60 patients included in the cohort, 15 POAF and 15 non-POAF patients were matched based on pre-operative characteristics. Gene set enrichment analysis of transcriptomic data from pre-operative EAT samples revealed 40 enriched biological processes in POAF vs non-POAF patients. Most of these processes were related to cellular immune response. Leukocytes (63±15% of total cells), and more specifically lymphocytes (56±13% of total CD45+ cells), represented the major cell subset in the preoperative EAT SVF, with no quantitative differences between POAF and SR patients (76 [52; 84]% vs 56 [50; 64]%, p=0.22). However, POAF patients presented a significantly higher cytotoxic CD8+/helper CD4+ T lymphocyte ratio than SR patients (respectively, 0.69[0.55; 1.19] vs 0.50 [0.31; 0.54], p=0.03) suggesting a cytotoxic shift prior to surgery. Conclusion: Epicardial fat from patients who develop POAF displays a specific pre-operative transcriptome signature characteristic of cellular immune response and cytotoxic lymphocyte enrichment. 30 matched samples analyzed (15 POAF vs 15 SR patients)