Congenital abnormalities of the conduction system in sudden death in young adults.

The sudden death of four apparently healthy young people, three men aged 25, 24 and 21 years, respectively, and one woman aged 20 years, was investigated. The heart was of normal size in two and was slightly enlarged in two. The conduction system in all hearts was serially sectioned. In all hearts the His bundle showed loop formation. In two, the branching bundle was left-sided with the right bundle branch intramyocardial. In the other two, the His bundle was markedly fragmented. Two had myocarditis, and three had arteriolosclerosis of the summit of the ventricular septum. These findings suggest the following: autopsy may be otherwise normal or show minimal findings in cases of sudden death in young people, with significant abnormalities seen only in the conduction system. The common denominator in the conduction system may be a congenital abnormality of the His bundle (in two hearts it was fragmented, in two it was left-sided and there was loop formation in all). Acquired changes may be present, such as arteriolosclerosis of the summit of the ventricular septum (three cases), myocarditis (two cases), and fatty infiltration in the atria (all four cases), a congenital abnormality of the His bundle with or without other findings (congenital or acquired) may cause reentrant phenomena or increased automaticity, ventricular arrhythmias and sudden death.