Surgical isolation of the XXXX from the atria. Identification of an atrial septal pacemaker.

@entity235 @entity943 @entity955
This is a report of the third in a series of experiments carried out to identify and to determine the reliability of atrial pacemakers below the sinoatrial (SA) node. This information could be useful to the surgeon in planning both corrective atrial operations and direct operations for @entity943 . In this study, done in @entity235 , the @entity955 containing the atrioventricular (AV) node was completely separated from the remaining atria. Seven @entity235 survived for 35 to 116 days. Serial electrocardiograms (ECGs) after operation showed that four of the seven @entity235 developed a regular junctional rhythm with a rate of 85 beats/min, whereas three of seven developed an irregular junctional rhythm with pauses and bigeminy. In a control study, in which the AV node was disconnected from the His bundle, a slow regular junctional rhythm was produced in all three of the @entity235 . Thus, in the series of three experiments, this being the report of the last one, a hierarchy of pacemakers below the SA node was identified. The first one, a pacemaker in the low right atrium in the region of the coronary sinus, was the most reliable and was associated with a normal ECG. A second, in the @entity955 , did not develop dominance in all @entity235 . However, the junctional pacemaker in the His bundle always became dominant after the AV node was disconnected from the His bundle and was associated with a regular but slow rhythm.
