Monophasic action potential recordings in response to graded hyperkalemia in dogs

EMANUEL. Monophasic action potential recordings in response to graded hyperkalemia in dogs. Am. J. Physiol. 256 (Heart Circ. Physiol. 25): H956-H961, 1989.-Recent interest in sud-den cardiac death during exercise in normal healthy people has highlighted the possible role of swings of extracellular potas-sium in arrhythmogenesis in conditions other than ischemia. Regional differences in action potential duration and conduc-tion may be important. We have recorded monophasic action potentials (MAPS) from the endocardium and epicardium in nine open-chest dogs during graded intravenous infusion of potassium up to a plasma level of 9 mM. The animals were anesthetized with a-chloralose and urethan. Continuous, on-line arterial potassium monitoring was employed. MAP dura-tion showed a biphasic response with initial shortening up to 7 mM, which tended to be more obvious on the epicardium