Repolarization Phase at Various Sites of the Right Atrium

Abstract

By means of a suction electrode method, the time course of depolarization and repolarization was observed in the in situ exposed right atrium of dogs. Under normal conditions the end of repolarization at various sites on the atrium occurred after the QRS spikes, and therefore, the T o wave should be inscribed after and not during the QRS spikes. The concentric spread of activation originating from the S-A node has been confirmed. The region of inital excitation does not become the initial focus of repolarization. The initial focus of repolarization is different from animal to animal, and this focus cannot be associated with any special cardiac tissue. The process of repolarization occurs concentrically from an initial focus that is not limited to any specific region of the atrium.

Direct Evidence of Nonuniform Distribution of Vagal Effects on Dog Atria

“…The factors causing variation in the APD of the right atrium in the dog heart in situ have been discussed previously. 10 In the present experiments, significant differences were noted in the APD between the right and left atrium ( Table 1). Such variation in duration may be due partly to the difference in temperature between the atria.…”

“…10 Since the coaxial suction electrode is flexible enough to follow the vigorous movement of the atrial surface, monophasic potentials could be recorded for a long time after applying negative pressure with a hydroaspirator. The changes in monophasic action potential detected by the recording electrodes were fed into a conventional high-grain differential d-c amplifier and displayed on a four-channel cathode ray oscilloscope (Model VC 7, Nihon Koden).…”