Differentiation of the atrioventricular conducting system of the heart

Development of atrioventricular specialized tissue in human heart

Images

Changes of myocardial enzyme activities in atrial fibrillation

Cholinesterase and succinyldehydrogenase activity of surgically removed left atrial auricles from patients in atrial fibrillation and in sinus rhythm have been compared, using histochemical methods. Higher cholinesterase and lower succinyldehydrogenase activity has been found in atrial fibrillation than in sinus rhythm. The pulmonary capillary mean pressure of patients with atrial fibrillation and sinus rhythm have been also compared. There was no significant difference between the two groups. On the basis of the reported examinations, it is not possible to decide whether the changes in enzyme activities are the cause or the result of atrial fibrillation.

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.