Formation of a border ischemic zone depends on plasma potassium concentration

Can J Physiol Pharmacol. 2023 Dec 20. doi: 10.1139/cjpp-2023-0304. Online ahead of print.ABSTRACTExtracellular potassium concentration might modify electrophysiological properties in the border zone (BZ) of ischemic myocardium. We evaluated the depolarization and repolarization characteristics across the ischemic-normal border under [K+] variation. 64-lead epicardial mapping was performed in 26 rats ([K+] 2.3-6.4 mM) in a model of acute ischemia/reperfusion. The animals with [K+]<4.7 mM (low-normal potassium) had an ischemic zone with ST-segment elevation and activation delay, a BZ with ST-segment elevation and no activation delay, and a normal zone without electrophysiological abnormalities. The animals with [K+] >4.7 mM (normal-high potassium) had only the ischemic and normal zones and no transitional area. Activation-repolarization intervals and local conduction velocities were inversely associated with [K+] in linear regression analysis with adjustment for the zone of myocardium. The reperfusion extrasystolic burden (ESB) was greater in the low-normal as compared to normal-high potassium animals. Ventricular tachycardia/fibrillation incidence did not differ between the groups. In patch-clamp experiments, hypoxia shortened action potential duration at 5.4 mM but not at 1.3 mM of [K+]. IK(ATP) current was lower at 1.3 mM than at 5.4 mM of [K+]. We conclude that the BZ formation in low-normal [K+] was associated with attenuation of IK(ATP) response to hypoxia and incre...
Source: Canadian Journal of Physiology and Pharmacology - Category: Drugs & Pharmacology Authors: Source Type: research