Conduction and Automaticity in Rat Myocardium

Intraventricular infusion of isotonic potassium chloride solution showed that blocking conduction in the subendocardial tissues of a single ventricle drastically alters normal conduction, with ensuing impulses being transmitted from the opposing ventricle. Blocking the endocardial tissues of both ventricles produces asystole even though the myocardium is capable of contracting as demonstrated by its contractile response to mechanical and electrical stimuli. These observations lend support to the concept that automaticity is a property confined to the specialized tissues of the conduction system.