2.1 Electrophysiological mapping in vivo
The achieved range of blood [K+] was from 2.33 to 6.42 mM. On the axis from the ischemic zone to the normal zone, two variants of the distribution of ATs and ARIs were observed at different levels of [K+]. In the animals with blood [K+] <4.7 mM (low-normal potassium), the affected area with ST-segment elevation was heterogeneous, and as a result three electrophysiological zones were discerned in the mapped area: an ischemic zone with ST-segment elevation and activation delay, a border zone with ST-segment elevation and no activation delay, and a normal zone without electrophysiological abnormalities. The animals with blood [K+] >4.7 mM (normal-high potassium) had only the ischemic and normal zones and did not have any transitional area (Fig.1). CV gradually decreased from the normal to ischemic zone in all animals (Fig.2).
The normal-high potassium animals had more pronounced activation delay (greater ATs) in the ischemic zone as compared to low-normal potassium animals (Fig.1), while ARIs were longer in the low-normal potassium rats in the normal, border, and ischemic zones (Fig.1, 3A). CV at lower [К+] was greater in all zones of myocardium as compared to CV at higher [К+] (Fig.2, 3B). It was found that the ARIs and CV were inversely associated with blood [K+] in linear regression analysis with adjustment for a zone of myocardium (B = -2.34 95% CI ‑3.448 – ‑1.284), p<0.001; and B = -0.024 95% CI -0.039 – -0.009, p=0.002, respectively) (Fig.3).
The extrasystolic burden at the 1st min of reperfusion was greater in animals with low-normal potassium (7.5±2.0 bpm) as compared to animals with normal-high potassium (1.2±0.4 bpm, p=0.006). Reperfusion ventricular tachycardia (VT) and fibrillation (VF) incidence did not differ between the groups (χ2 = 0.079, p=0.779).