Histamine and cardiac arrhythmias.

Modification of the cardiac rhythm by histamine has been appreciated almost since the compound's isolation from ergot by Barger and Dale in 1910. The major arrhythmogenic actions of histamine are an Hi-receptor-mediated slowing of atriovenrricular (AV) conduction and H2-receptor-mediated increases in sinus rate and ventricular automaticity. These actions were elucidated by observing the salutary effects of histamine antagonists on the arrhythmias of anaphylaxis, and by administering exogenous histamine to various cardiac preparations in the presence and absence of histamine antagonists. The ability to record transmembrane action potenrial(s) (TAP) from single cells has permitted the study of electrophysiological mechanisms underlying histamine-induced arrhythmias.