Complete atrioventricular block with intact retrograde conduction due to a concealed extranodal anomalous pathway

Patients with advanced or complete heart block occasionally manifest intact retrograde conduction. It has usually been postulated that such patients have lesions of the conduction system that produce unidirectional block. There has been some electrophysiologic evidence supporting that hypothesis. In this report, a patient with complete heart block and intact retrograde conduction is described. Electrophysiologic studies demonstrated that retrograde conduction was via a concealed extranodal anomalous pathway.