EPHB4 and atrial fibrillation: In contrast, the signaling activity of EC in AF underwent significant alterations, particularly in autocrine signals (e.g., VEGF–VEGFR, EFNB/A1–EPHB4), which were absent in AF, whereas signals from EC to LBCs were markedly elevated, suggesting that the role of EC in AF may have shifted with respect to interactions with other cell types.