Abstract
A histopathologic study based on serial sections of the conduction system was performed on 31 cases with chronic advanced or complete atrio-ventricular (AV) block. The patients were divided into 3 groups according to the injured portion of the conduction system: group 1 with lesions in the AV node or its approach, 4 patients; group 2 with lesions in His bundle, 10 patients; and group 3 with lesions of bundle branches and/or His bundle, 17 patients. The frequency of lesion site agreed with other reports. Fibrosis of the conduction system has been reported as the cause of conduction disturbance, but the etiology has not been made clear. In group 1, peri-cardial inflammation was seen in 3 of 4 cases. In group 2, inflammatory infiltration was noted in only 2 cases. Idiopathic fibrosis of conduction tissue or calcification of the AV ring was evident in 6 of 10 cases. In group 3, not only Lev disease and Lenègre disease but also perimyocarditis and its sequela were seen. Perimyocarditis and its sequela could be observed in 9 of 17 cases. Therefore, the occurrence ratio of perimyocarditis was higher than anticipated.
