Myocardial oxidative stress is increased in early reperfusion, but systemic antioxidative therapy does not prevent ischemia-reperfusion arrhythmias in pigs

Figure 1. Illustration of the experimental protocol, and evidence of myocardial oxidation in early reperfusion. (A) Timeline in minutes for the ischemia-reperfusion protocol used for pig myocardial infarction (MI) experiments. (B) Oxidative stress during ischemia and reperfusion. Top panel: Western blot of MDA levels in protein lysates from biopsies taken at baseline, 5 min reperfusion Ctrl and 5 min reperfusion NAC. Bottom panel: Western blot of MDA levels in protein lysates taken at baseline and 60 min reperfusion from the infarct zone (IZ), border zone (BZ) and remote zone (RZ). Bottom panel: Western blot of 3NT levels in protein lysates taken at baseline and 60 min reperfusion from the infarct zone (IZ), border zone (BZ) and remote zone (RZ). (C) Quantification of MDA at Baseline, 5 min reperfusion and 60 min reperfusion from the infarct zone (IZ). MDA levels were significantly increased at 5 min reperfusion compared with baseline (p = 0.0462, One way ANOVA with Šidák's correction for multiple comparisons). Baseline (N = 11), 5 min reperfusion (N = 11, 6 Ctrl/5 NAC), 60 min reperfusion (N = 8). (D) Quantification of MDA levels at 5 min reperfusion in Ctrl and NAC samples. No…

Figure 2. Circulating biomarkers for myocardial injury. (A–F) Bar graphs show the levels of Troponin T at baseline, ischemia and 60 min reperfusion, and levels of ALAT, ASAT, CK, LDH and myoglobin at baseline, ischemia, 5 min reperfusion and 60 min reperfusion in Ctrl and NAC pigs. There was a significant increase in all markers of myocardial damage with time: Troponin T (p = 0.0005), ALAT (p = 0.0111), ASAT (p < 0.0001), CK (p < 0.0001), LDH (p = 0.0002) and Myoglobin (p < 0.0001), Mixed-effects analysis with Geisser-Greenhouse correction. Treatment with NAC had no significant effect on markers of myocardial damage (Mixed-effects analysis with Geisser-Greenhouse correction) MI Ctrl = 6 pigs, MI NAC = 5 pigs.

Figure 3. Electrocardiogram (ECG) examples and temporal arrhythmia incidence in ctrl pigs during ischemia-reperfusion. (A–D left panel) ECG example tracings from lead II of 12-lead ECG of IVR, NSVT, VT and VF. IVR = Idioventricular rhythm (>30 s), NSVT = Non-sustained ventricular tachycardia (<30 s), VT = Ventricular tachycardia (>30 s), VF = Ventricular fibrillation. (A–D right panel) Bar graphs show the temporal incidence of IVR, NSVT, VT and VF during ischemia reperfusion in MI Ctrl pigs. Data is presented as number of arrhythmic episodes per pig. One pig died after 20 min ischemia, and is therefore only included up until this time point. MI Ctrl ischemia 0–20 min =7 pigs, MI Ctrl ischemia 20 min–60 min reperfusion = 6 pigs.

Figure 4. The effect of NAC on reperfusion arrhythmias. (A–C) Bar graphs show the incidence of IVR, NSVT and VT and in Ctrl and NAC groups at 15 min intervals of reperfusion, presented as number of arrhythmic episodes per pig. Treatment group (Ctrl and NAC) had no significant effect on the incidence of IVR, NSVT or VT (Mixed-effects analysis with Geisser-Greenhouse correction). Time had a significant effect on the number of NSVT episodes, with more episodes occurring during early reperfusion (p = 0.0052, Mixed-effects analysis with Geisser-Greenhouse correction). (D) Bar graphs show the total number of IVR, NSVT and VT episodes per pig during 60 min reperfusion. No significant differences were observed for the incidence of total IVR, NSVT or VT between Ctrl and NAC animals (Mann-Whitney test). MI Ctrl: N = 6 pigs, MI NAC: N = 5 pigs.