[Identification of the sino-atrial potential in the dog by epicardial electrocardiography].

The electrical activity of the sino-atrial node has been recorded in the dog through a thoracotomy and using both unipolar and bipolar electrodes. Amiodarone was used to establish that the pre-artial potential which was registered was indeed originating in the sinus, as it allowed us to produce various degrees of sino-atrial block in a reliable and reproducable manner. The fact that the sinus potential can be recorded in the presence of intermittent abnormalities of the surface P wave suggests that the abnormalities may be associated with intra-sinus displacement of the pacemaker and not with ectopic depolarisation of the atrium.