CYBB and heart failure: The angiotensin system and TGF‐β1 play an important role in atrial fibrosis‐associated with the heart failure models of AF,29, 30 a mouse model of AF30 and in human AF associated with heart failure.31 Ang‐II can stimulate NADPH oxidases 2 (Nox2) activity through the TGF‐β1 pathway and inhibition of TGF‐β1 blunts reactive oxygen species (ROS) formation.32, 33 Therefore, renin–angiotensin–aldosterone system (RAAS)–induced TGF‐β1 pathway and TGF‐β1–induced ROS may contribute to fibrotic remodelling.