Ischemic but not reperfusion arrhythmias depend upon serum potassium concentration

The effects of variations in serum concentrations of potassium on the occurrence and severity of ischemia- and reperfusion-induced arrhythmias have been studied in conscious rats. Serum potassium concentrations were modified by maintaining rats on diets which varied in potassium concentration, by treatment with hydrochlorothiazide, amiloride, spironolactone or infusions of potassium chloride. An inverse linear relationship was demonstrated between ischemia-induced arrhythmias and log(e) serum potassium concentration such that a 50% reduction in arrhythmias occur with a 3.8-fold increase in serum potassium concentration. On the other hand, the incidence of reperfusion-induced arrhythmias after 7 min of regional ischemia prior to reperfusion in previously untreated rats were not influenced by elevation of serum potassium concentrations prior to and after reperfusion. Effects on ischemia-induced arrhythmias could not be explained by changes in blood pressure or heart rate. It is speculated that modification of potassium concentration in non-ischemic or border zone ventricular tissue may directly modify arrhythmogenesis due to ischemia but not that due to reperfusion.