CD74 and atrial fibrillation: Our previous study revealed that MIF increases atrial arrhythmogenesis through CD74 signalling by increasing the calcium (Ca2+) transient, sarcoplasmic reticulum (SR) Ca2+ content, Na+/Ca2+ exchanger (NCX) efflux rates, and level of Ca2+ leak.4 The pulmonary vein (PV) receives the most attention during AF initiation and maintenance.5 Macrophage migration inhibitory factor signalling activation was hypothesized to regulate PV arrhythmogenesis, contributing to AF genesis during inflammation.