Cyclic A.M.P. and arrhythmias revisited.

Further evidence is presented for a hypothesis linking cyclic adenosine 3', 5' monophosphate (cyclic A.M.P.) and arrhythmias: in the isolated rat heart, changes in tissue cyclic A.M.P. are accompanied by changes in the ventricular-fibrillation threshold; and in the pig, large infarcts are associated with raised tissue cyclic A.M.P. and ventricular fibrillation, whereas small infarcts are not. Data showing that changes in the metabolism of potassium, glucose, fatty acids, and lactate can influence the action-potential duration are incorporated into a revised hypothesis which allows for multifactorial arrhythmogenic mechanisms in the early stages of acute myocardial infarction.