The landmarks to the atrioventricular conduction system in hearts with absence or unroofing of the coronary sinus.

Histologic studies were made of the conduction system of two hearts, one with absence and the other unroofing of the coronary sinus. The findings show that, when present, the triangle of Koch and the orifice of the coronary sinus are usually good guides to the atrioventricular conduction axis. However, when these landmarks are malformed, or there is malalignment of the atrial and ventricular septal structures, a better guide is the fusion point of the ventricular septum with the atrioventricular junction.