P357 Remote ischemic post-conditioning may prevent cardiac remodeling within two years of STEMI by cardioprotective microRNA upregulation

Abstract Background Remote ischemic post-conditioning attenuates ischemia-reperfusion injury in patients with STEMI. However, its biochemical mechanisms, including micro-RNA expression, and effects on cardiac remodeling have not been defined. Methods We examined 80 patients with STEMI and 20 healthy controls. All patients had been evaluated by cardiac echocardiography. The conditioning protocol utilised a single ischemic stimulus by brachial cuff inflation of both arms at 200mmHg for 5 minutes, while 20 patients underwent a sham conditioning procedure by way of cuff inflation omission after its placement. Blood samples were taken before and after the conditioning protocol; thus, the expression of microRNA-144,-150,-499 (cardioprotective action), -21, and -208 (remodeling stimuli) was quantified at baseline and after the ischemic conditioning procedure, by polymerase chain reaction. Additionally, cardiac remodeling was evaluated by repeat echocardiography after a 2-year follow-up period, in 40 patients. Results Our conditioning protocol resulted in a statistically significant increase in miR-144,-150, -499, -21, and -208 expression (55.9 vs 7.4/U6sn, p < 0.001; 3.4 vs 1.8/U6sn, p < 0.05, p = 0.01; 3.5 vs 1.6/U6sn, p < 0.001; 2.1 vs 1.2/U6sn; 2.4 vs 1.9/U6sn) compared to baseline; none of the aforementioned measurements was affected by the sham procedure. Furthermore, both left-ventricular end-diastolic (LVEDV) and end-systolic volume (LVESV) were decreased after the 2-year follow-up period (from 99.3 ± 6.7 to 85.9 ± 5.7, p= 0.004, and from 55.3± 6.1 to 48.6± 5.2, p= 0.04, respectively). In addition, the increase in mir-144 and mir-499 was significantly correlated with a decrease in LVESV (r=-0.355, p < 0.05; r=-0.368, p < 0.05, respectively), while the increase in mir-499 was also significantly correlated with a decrease in LVEDV (r=-0.374, p < 0.05) at follow-up. Conclusion Remote ischemic conditioning may prevent adverse myocardial remodelling within 2 years of the index ischemic event, likely by up-regulation of cardio-protective microRNAs expression.