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 concentr ation ([K+](o)) and extracellular pH (pH(o)) exist. In globally ischem ic papillary muscles increased Pco(2), causes a rise in [K+](o). We st udied whether pH(o) and [K+](o) are causally related during acute regi onal ischemia in the isolated blood-perfused pig heart. Multiple pH- o r K+-sensitive electrodes were inserted in the left ventricular midmyo cardium, Local electrograms and ionic data were simultaneously acquire d. Regional ischemia was produced by interrupting left anterior descen ding (LAD) artery now (10 min). Up to 5 mm from the electrophysiologic al border the pH-K relation deviated from that in the central ischemic zone. Respiratory acidosis (pH about 7.10) of the perfusate in the pr esence of LAD-ischemia caused acidification of the ischemic border zon e without a local change in [K+](o). We conclude that pH(o) changes ar e not related to changes of intramural [K+](o) in the lateral border z one during regional ischemia. (C) 1995 Academic Press Limited