Histopathological study of the conduction system of the heart in Duchenne progressive muscular dystrophy.

The cardiac conduction systems including sinoatrial (SA) node, atrioventricular (AV) node, atrioventricular(His) bundle, and peripheral conduction system (left and right bundle branch, and Purkinje fiber) of 23 patients with Duchenne progressive muscular dystrophy(DMD) were studied with light microscope. Infiltration of fat tissue and mild fibrosis were occasional findings in SA and AV nodes. Degeneration of the conduction muscle fiber was hardly noted in SA node, AV node, and His bundle. Only the peripheral conduction system (Purkinje fiber) showed significant degenerations such as eosinophilic, necrotic and vacuolar changes with fibrosis. These necrobiotic changes resembled hyaline and vacuolar skeletal and cardiac muscular degenerations in DMD and were assumed to have occurred on the basis of the structural and constitutional characteristics of the peripheral conduction fiber as a striated muscle fiber. The vascular changes and amyloid deposit suggesting precocious aging in the conduction systems were not observed.