PDCD1 and atrial fibrillation: Analysis of T cell subsets identified an increase in TRM cells, as defined by high expression of CD69 and the inhibitory molecule programmed cell death 1 (PD1) receptor, in the EAT of patients with AF compared to SR (Fig. 1a and Extended Data Fig. 2a), which was accompanied by a decrease in CD69− memory T cells (Extended Data Fig. 1e).