Perfusate potassium: Effect on ischaemia-induced arrhythmias in pre-conditioning in isolated rat heart

The aim of our study was to investigate whether perfusate potassium concentration alters the effects of preconditioning on early ischaemia-induced arrhythmias. Rat hearts (n = 12, each group) were Llangendorff-perfused with Krebs-Henseleit solution with different K+ concentrations. A ligature around the left anterior coronary artery was used to cause regional ischaemia. Hearts were randomised into three control groups (K+ 2.5 mmol L(-1), K+ 4.0 mmol L(-1) K+:6.0 mmol L(-1)) which underwent 15 min ischaemia and into three pre-conditioned groups (K+:2.5 mmol L(-1), K+:4.0 mmol L(-1), K+:6.0 mmol L(-1)) in which the 15-min ischaemia was preceded by two cycles of 3 min ischaemia and 5 min reperfusion. During ischaemia, ventricular tachycardia occurred in 100% (K+ 2.5 mmol L(-1)), 100% (K+ 4.0 mmol L(-1)) and 50% (K+ 6.0 mmol L(-1)) of the control groups versus in 100%, 33% (p < 0.05) and 25% of the pre-conditioned groups respectively. Ventricular fibrillation occurred in 83% (K+ 2.5 mmol L(-1)), 41% (K+ 4.0 mmol L(-1)) and 16.7% (K+ 6.0 mmol L(-1)) of the control groups and in 33% (p < 0.05), 16.7% and 0% of the pre-conditioned group respectively. Our data confirms that pre-conditioning affords protection against early ischaemia-induced arrhythmias in the isolated rat heart. They also show that low perfusate potassium appears to increase the threshold for pre-conditioning against ischaemia-induced arrythmias.