[Types of pathomorphological changes in the heart caused by cardiostimulating electrodes]

Reaction at the site of pacemaker electrode was examined at post-mortem by morphological and histological means in a group of 18 deceased patients with pacemakers implanted through the endovasal channels. The changes were classified into 5 basic types depending on their nature and rate of incidence: changes in the endocardium (connective tissue bridging of the electrode, and changes in the tricuspid valve) and in the myocardium (electrode penetration, reaction under the tip of the electrode, and no changes). The particular types occurred either independently of each other, in in mutual combination. Electrode fixation to the endocardium by means of connective-tissue organizing wall thrombi was found in 97% of all the cases examined. There was no unambiguous proof of the duration of pacemakers electrode implantation as being directly dependent on the extent of connective tissue bridging of the electrode. There were exceptional cases of malacia or scars in the myocardium under the tip of the electrode in the normal position of the electrode in patients with myocarditis.