The relation between extracellular potassium concentration and pH in the border zone during regional ischemia in isolated porcine hearts

During regional ischemia gradients of extracellular potassium concentration ([K+]0) and extracellular pH (pH0) exist. In globally ischemic papillary muscles increased Pco2 causes a rise in [K+],. We studied whether pH0 and [K+]0 are causally related during acute regional ischemia in the isolated blood-perfused pig heart. Multiple pH− or K+-sensitive electrodes were inserted in the left ventricular midmyocardium. Local electrograms and ionic data were simultaneously acquired. Regional ischemia was produced by interrupting left anterior descending (LAD) artery flow (10 min). Up to 5 mm from the electrophysiological border the pH-K relation deviated from that in the central ischemic zone. Respiratory acidosis (pH about 7.10) of the perfusate in the presence of LAD-ischemia caused acidification of the ischemic border zone without a local change in [K+]0. We conclude that pHo changes are not related to changes of intramural [K+]o in the lateral border zone during regional ischemia.