Circadian variations of infarct size and inflammation response in patients presenting a STEMI

Introduction Circadian rhythm modulates many physiological functions. Some studies suggest a circadian variation of infarct size (IS) in experimental models and in human. It is also known that inflammation is modulated according to circadian rhythm. Inflammation has a central role in post-MI remodeling and final IS. Circadian variation of IS and inflammation response after MI are unknown. Objective Our objective was to evaluate the modulation of IS according to the reperfusion time of the day and to assess if post-MI inflammation was also modulated by circadian rhythm. Method In our biobank, we selected 115 patients who presented with a ST-elevated Myocardial Infarction (STEMI). Two groups were done according to the reperfusion time of day. The morning group (MG) was reperfused between 6:01 am and 12:00 and the afternoon group (AG) was reperfused between 12:01 and 6:00 pm. Each patient had a blood sample upon admission and 4 hours after reperfusion. IS was assessed using cardiac magnetic resonance (MRI) imaging. Main inflammatory markers as interleukin (IL)-6, IL-8, IL-10 and C-reactive protein (CRP) were dosed using ELISA. Results There were 53 patients in the MG and 62 patients in the AG. Patients characteristics were similar in the two groups, especially ischemia time (median of 165 min in both groups). We observed that IS assessed by MRI was significantly reduced by 23.2% in the AG compared to the MG ( P  = 0.04). Furthermore, patients reperfused the afternoon showed a less intense inflammation reaction post-MI with a 54% decrease of CRP ( P  = 0.004) and 30% decrease of IL-6 ( P  = 0.047) compared to the MG. IL-8 and IL-10 levels were similar in the 2 groups. Conclusion We confirmed a circadian variation of myocardial IS in STEMI reperfused patients according to the reperfusion time of the day. The largest IS was observed in the MG. CRP and IL-6 were also modulated according to circadian rhythm with a higher level the morning compared to the afternoon.