Studies on the Spread of the Right Atrial Activation by Means of Intracellular Microelectrode

Intracellular action potentials and the spread of the excitation in the right atrium were investigated on a whole specimen of a dog's or rabbit's right atrium by means of microelectorde method. The excitation was originated at a certain point of sinoatrial node and was transmitted very slowly in all directions in the node. The sinus excitation was transmitted rapidly through crista terminalis being transmitted to mm. pectinati. The atrial roof was activated by the stimuli coming from mm. pectinati. The thicker the muscle bundle, the faster the conduction and the longer the action potential duration. Conduction rate of the excitation through crista terminalis was about 1.5 meter per second and that in sinoatrial node was about 0.1 meter per second. The author could not observe any highly differentiated specific conduction system in the atrium like His' bundle or Purkinje fiber in the ventricles.