HIF1A and sleep apnea syndrome: Expressions of HIF-1α, Grp78 (the main ER stress sensor) and CHOP (the terminal pro-apoptotic factor of the unfolded protein response), in human atrial appendage biopsies of patients with sleep apnea (AHI > 22 ± 2 events.h−1) and in hearts from rodents exposed to chronic intermittent hypoxia are presented in Figure 2.