Sympathetic neural mechanisms in cardiac arrhythmias

In the present experiments the dominant role in the genesis of arrhythmias of stimulation of beta adrenoceptors over that of alpha adrenoceptors has been demonstrated by: (i) infusion of catecholamines in the isolated right ventricular Purkinje fiber preparation of rabbits; and (ii) by subepicardial microinfusion of these substances to anesthetized thoracotomized dogs. Activation of the latent pacemaker areas by local myocardial ischemia was shown. Catecholamine-induced arrhythmias also resulted from premature excitation of the working myocardium as a consequence of an interaction of Purkinje firing and excitation originating from higher pacemaker areas.