Histopathological study on the conduction system with complete atrioventricular block--with special reference to configuration of QRS complex.

Abstract

The conduction system of 14 autopsied hearts with complete AV block, was examined with the serial sectioning method and the following results and conclusions were obtained. (1) The lesion at the upper AV conduction system covering from the AV node and its approaches to the proximal branching portion of the bundle of His mainly corresponded to the complete AV block with narrow QRS complex (5/6). On the contrary, the lesion at the lower AV conduction system in or distal to the branching portion of the bundle of His fully corresponded to the complete AV block with wide QRS complex (8/8). (2) An exceptional case had the lesion at the distal penetrating portion of the bundle of His which corresponded to the complete AV block with wide QRS complex and the complete right bundle branch block with left axis deviation during sinus rhythm. This case could be explained by the anatomical longitudinal dissociation in the bundle of His. (3) Correlation of the HBE and histological findings was studied in 4 cases. There were 2 cases with AH block and narrow QRS configuration; one case had the lesion in the AV node and its approaches and the other had the lesion at the proximal branching portion of the bundle of His. There were 2 cases with HV block and wide QRS complex; one case had the lesion at the branching portion of the bundle of His and the bundle branches and the other had the lesion only at the bundle branches. (4) In EKC, the so-called trifascicular pattern was observed in 6 cases. Three among the 6 cases had main lesions of the bundle branches. An one case among the 6, had coexisting lesions at both the portions of the bundle of His and the bundle branches and the remaining one had the lesion at the distal penetrating portion of the bundle of His. (5) Moderate to severe reduction of the conducting cells lesion was observed in some level in the AV conduction system in all case studied. Especially severe reduction of conducting cells was observed in all case having permanent complete AV block with long duration. (6) Etiologies of the complete AV blocks were assumed as follows; 6 senile degeneration type, 3 acute myocardial infarction, 2 chronic ischemia, 1 congenital malformation, 1 metastatic neoplasm and 1 of uncertain cause.