Conduction System in a Trained Jogger with Sudden Death

A 47-year-old extremely active, entirely asymptomatic trained jogger was found dead in bed. He was known to have had sinus bradycardia with first-degree atrioventricular block for eight years and a type 1 second-degree block five years prior to death. A permanent pacemaker had been inserted, and apparently the patient was then in good health and maintained his jogging program until he died suddenly. The conduction system revealed an atrioventricular node situated more to the left of the atrial septum than usual, which made tenuous connection with the surrounding atria due to marked fatty infiltration. The atrioventricular node as it joined the left-sided His bundle revealed fatty metamorphosis, fibrosis, disarray of myocardial fibers, and mononuclear cell infiltration. The right bundle branch was intramyocardial and fibrosed throughout. Increased aging changes of the left side of the septum with arteriolosclerosis and patchy fibrosis were present. This is the first case in which the atrioventricular node was more to the left side of the atrial septum with fatty separation of the node from the surrounding atrial musculature, with myocardial disarray of the nodal-His bundle junction. Although congenital abnormality of the conduction system may remain silent without symptoms for a long time, it should be kept in mind that sudden death may occur sooner or later in some susceptible individuals.