Abstract
The incidence of ventricular fibrillation (VF) was compared to the degree of shortening of ventricular myocardial effective refractory period (ERP) produced by sympathomimetics Epinephrine (E) and norepinephrine (NE) markedly shortened ERP (58.3 and 60.9 %, respectively), and produced VF in 100 % of the cases. The other which slightly shortened ERP: Mechanism of arrhythmia isoproterenol (20.6%), phentetramine (11.8%), and phenylephrine (7.6%) did not produce VF. <i>α</i> (‘Se 2’, dibenamine) and <i>β </i>(propranolol) adrenergic blocking agents (ABA) antagonized both VF and ERP shortening. Their relative pharmacological potencies were comparable both in antagonism towards ERP shortening and VF produced by E or NE. Both phenomena are thus intimately connected. Such sympathomimetic actions could not be classified either as <i>α</i> or <i>β, </i>exerted upon an admittedly special <i>Ε</i>-adrenergic receptor inspecific as to its blocking and different from the mediator of inotropic and chronotropic positive actions of sympathomimetic agents.
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