Sudden death caused by benign tumor of the atrioventricular node

Histologic study of the conduction system of the heart of a 16-year-old girl who died suddenly demonstrated a benign mesothelioma of the AV node, with almost complete replacement of the structure by the tumor. Teh past history was unremarkable, except for few syncopal episodes at 9 and 11 years of age and during pregnancy. Immediately postpartum, she developed a 2:1 AV block and intermittent complete AV block. Six weeks later, during diagnostic work-up in the cardiac catheterization laboratory, she died suddenly. Electrophysiological studies during this work-up disclosed complete AV dissociation, with normal QRS complexes. The block was proximal to the His-bundle recording site, with a normal H-V interval. Occasional syncopal attacks in young adults should alert the physician to the possibility of this diagnosis and lead to pacemaker insertion.