HIF1A and atrial fibrillation: By interrogation of apoptosis arrays we were able to show that a number of transcription factors associated with an oxidative stress response were upregulated in response to AF, including hypoxia inducible factor 1-alpha (HIF-1α), heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2) (Figure 5C).