The TLR4/CaMKII signalling pathway has been reported to play an important role in atrial arrhythmia through regulating atrial fibrosis, inflammation, and the function of calcium‐handling proteins.14, 28 Besides, according to our previous studies, MD1 has a suppressive effect on TLR4/CaMKII signalling pathway.17, 29 Thus the TLR4/CaMKII signalling pathway was investigated to confirm the function of MD1. Here, TLR4 is linked to fibrosis.