Atrioventricular node fetal dispersion and His bundle fragmentation of the cardiac conduction system in sudden cardiac death

Objectives. This study sought to examine the frequency of persistent fetal dispersion of the atrioventricular (AV) node and fragmentation of the atrioventricular bundle (His) bundle in the cardiac conduction system of sudden cardiac death cases and control subjects to establish their importance as the cause of death. Background. These are two of the most frequent lesions reported in published reports in the cardiac conduction system in unexplained sudden deaths. Methods. We have studied the conduction system of 347 hearts: 249 hearts from sudden cardiac death cases and 98 control hearts. The sudden cardiac death cases were divided, according to the pathology found, in three groups: group I: ischemic heart disease, 137 cases; group II: nonischemic heart disease, 48 cases, and group III: unexplained sudden cardiac deaths, 64 cases. The control group (group IV) consisted of patients with unnatural deaths and extracardiac natural deaths. Results. Persistent fetal dispersion of the AV node was observed in 70 cases (20.17%) of all groups with frequency (40.81%) statistically higher in the control group. Fragmentation of the His bundle was observed in 95 cases (31.77%), and the frequency was statistically higher in the control group, too (47.67%). Conclusions. Persistent fetal dispersion of the AV node and fragmentation of the His bundle can be normal variation present during many years in life and must not be considered the anatomic substrate for arrhythmias and sudden death without electrocardiographic abnormalities.