LAUSR

Introduction Congenital heart block (CHB) has long been associated with maternal anti-SSA/Ro antibodies. Injury to the conduction system is presumed to be a consequence of the transplacental passage of maternal IgG autoantibodies into the fetal circulation. Within the heart, a spectrum of phenotypes has been described, including structural defects, functional abnormalities, and electrical disturbances such as heart block. Thirddegree atrioventricular (AV) block is typically irreversible, has a mortality rate approaching 30%, and requires pacemaker placement in up to 66% of cases. Autopsies of cardiac specimens from individuals with CHB have demonstrated the absence or partial absence of internodal and interatrial pathways. Disruption of the structure of Bachmann’s bundle, the major interatrial pathway, can result in interatrial dissociation in which each atrium beats independently. Under this circumstance, the right atrium (RA) is under the control of the sinus node, while the left atrium (LA) is under the control of an ectopic pacemaker. We describe a newborn with complete CHB in the setting of maternal anti-SSA/Ro antibodies in whom interatrial dissociation was recognized after placement of a dual-chamber epicardial pacemaker system with bipolar LA and left ventricular (LV) pacing leads.