[An experimental study on the influence of surgical injuries to the internodal conduction tracts on supraventricular arrhythmias associated with intraatrial operations].

In this study, the relationship between injuries to the internodal conduction tracts and supraventricular dysrhythmias was investigated in 30 adult mongrel dogs. Conduction time from the SA node to the vicinity of the AV node and isochronous activation sequences were examined by endocardial mapping during cardiopulmonary bypass before and after surgical injury to the anterior, middle or posterior internodal tracts. Prior to injury, the impulse from the SA node was conducted rapidly along the crista terminalis and the anterior arch of the crista. Only when the anterior internodal tract was injured, regardless of the location and the numbers of injuries, the conduction time from the SA node to the vicinity of the AV node was prolonged significantly, about 15 msec. After sequential division of the tracts, the cardiac rhythm was observed: Division of the anterior and posterior internodal tracts, or all the three tracts resulted in the absence of sinus rhythm and the appearance of brady-arrhythmias such as AV junctional rhythm in about fifty percent of the dogs. These findings suggest the importance of preservation of the anterior or posterior internodal tracts during intraatrial operation.