Anatomy of the Atrioventricular Conduction System in Ventricular Septal Defect

The major parts of the atrioventricular conduction system of the human heart were traced in 21 instances of ventricular septal defect: 19 were examples of variously located uncomplicated ventricular septal defects and two of the tetralogy of Fallot. In the presence of a ventricular septal defect, the conduction system was found to have a normal course, except when the ventricular septal defect lay in a position normally occupied by the conduction system. In each specimen with a defect posterior and inferior to the crista supraventricularis, the conduction system occupied a position posterior and inferior to the defect. In no instance did the conduction system occupy a position superior to a defect of this type. Defects located in the posterobasal portion of the muscular part of the ventricular septum sometimes were posterior to the main parts of the conduction system, so that the conduction tissue was related to the anterior edge of the defect. No example of a defect lying superior to the crista supraventricularis was studied. In our two examples of tetralogy of Fallot, the position of the conduction system was essentially similar to that occurring in the usual variety of ventricular septal defect, that is, posterior and inferior to the crista supraventricularis.