Abstract
The pathological changes of the conduction system which involve in aging process has attract much attention of the cardiologists as it may lead to unexpected clinical death, however, scanty morphological observation of it has been hitherto documented.
Moreover the interrelationship between the degenerative process of the cells composing the conduction system and extent of the arterioscerosis of the distributing vessels should awaits further confirmation.
In this viewpoint, the authors have conducted an investigation of the histo-pathologic pattern of the various portion of the conduction system (Sinus node, A-V node, bundle branches in 32 cases varying in various age group which are devoid of any discernible heart diseases.
Observation:
The decrease of the cell population in the sinus node, A-V node and His bundle is observed in age group of beyond fifty without exception.
The pathological changes involving the both bundle branches remained to be a lesser extent, however, gradual involutional changes are discernible beyond sixty.
The authors failed to confirm the arteriosclerotic changes of the small arteries, particularly of sinus node artery which give supply to the sinus node and other arteries giving supply to the region beneath the A-V node on aging.
In some cases which are involved in relatively remarkable degeneration and loss of cells of the conduction system, rather intensive lipid infiltration in the medial layer, however, the extent of the myocardial fibrosis remained to be a lesser extent which are obviously substantiated with the ultrastructural observation.
The facts may not be justifiable as the reflect of ischemic process and some abnormalities of the intermediate metabolism involving the lipid and associated substances should be taken into the consideration.
In the group which showed arteriosclerosis and loss of the cells revealed remarkable fibrosis while the lipid infiltration remained to be minimal range.
The ultrastructural observation revealed disintegration of the myocardial fibrils, accumulation of lipid, swelling of the endothelial cells of the capillary vessels and fragmentation of the basal lamina.
Koizumi and Yajima has observed the scerotic changes of the small arteries distributing the conduction system in cases of ventricular septal defect and Tetroalgy of Fallot which may suggest a possibility that the circulatory derangement would be very important contributing factor for direct causing of ischemic process.
In this vicinity the authors incline to believe that the less extent of the screlotic changes in aged conduction system could be explained on based that the ischemic changes in this region is hardly taken placed on account for the specific anatomical distributing pattern of the blood supply.
The authors conclusively would like to place an emphasis on a possibility that the sclerotic changes of the small vessels distributing the conduction system is rather hardly recongnizable without concomitant occurence of the micro-circulatory derangement in this particular region.
The patho-physiological aspect of this microcirculatory derangement is fully augmented in this communication in connection with the arteriosclerotic process, involving the cells and vasculature of the conduction system per se.
