Wagner and Hall (1967) reported 2 brothers and a sister with congenital atrioventricular dissociation. They emphasized that this is distinct from A-V block. In dissociation the abnormality seems to be 'lazy' sinoatrial pacemaker with the A-V node taking over intermittently by default. In A-V block an impediment to A-V conduction exists. See heart block (113900, 140400, 234700) and nodal rhythm (163800).