[Sudden death as a result of conduction disturbances. Part I. Quantitative pathology of conduction and conduction disorders].

This quantitative histological study of the conduction system comprises 57 patients showing electrocardiographically documented conduction disturbances. In the sinu-atrial node of all patients with sick sinus syndrome the ratio of specific cells to connective tissue shows a shift in favour of connective tissue. In most patients with permanent complete atrio-ventricular block, we found a lesion destroying three quarters of the fibres at one level at least of the av-node or the main bundle. These criteria are used to investigate the conduction system of patients dying suddenly and unexpectedly. A ratio of specific cells to connective tissue below 0.2 in the sinu-atrial node is highly suggestive of nodal dysfunction. A lesion of the av-node or the main bundle comprising three quarters of the whole structure is nearly always accompanied by av-block. If such a lesion in the conduction system is the only pathological autopsy finding, the cause of death is most probably cardiac arrest due to this lesion.