After comparing left atrialsamples from patients with paroxysmal, persistent, and permanent atrialfibrillation to those with sinus rhythm, Xu et al. [17] found that theexpression of HIF-1α in the left atrial tissues of patients withpersistent or permanent atrial fibrillation was increased compared to those withparoxysmal atrial fibrillation or sinus rhythm. Here, HIF1A is linked to atrial fibrillation.