[Recording of the electrical activity of the sino-atrial node area during an experimental sinoatrial block in dogs. Arguments in favor of its sino-atrial origin].

The electrical activity of the sino-atrial node appears to be difficult to detect, and has not until now been recorded from the heart in situ. Recording of the electrical activity from the area of the sino-atrial node area was carried out in the dog after thoracotomy, using a unipolar electrode placed in the epicardium at the cavo-atrial junction area; it enabled us to demonstrate a slow potential, of low amplitude, preceding the atrial deflection. The particular relationships between this slow potential and atrial activity under differing degrees of sino-atrial block have led us to believe that this potential does indeed originate in the sinoatrial node. In the light of this experimental observation, an explanation is put forward for the difficulty which is usually experienced in obtaining any recording of the sino-atrial node potential, and for the ease with which this potential could be recorded in this case, and indeed in future cases with similar pathological problems.