Histologic evaluation of the atrioventricular nodal artery in healthy humans and in patients with conduction disturbances.

The anatomy of the conduction system of the heart so relevant in the contemporary invasive cardiology is not fully understood. It has turned out that ablation procedures bring new information as to its structure and function, but in some cases can result in complete a-v block. Atrioventricular nodal artery located within the nodal-perinodal tissue can probably be damaged during the ablation procedures. Therefore, we decided to explore in detail the morphology and the topography of the atrioventricular nodal artery in healthy humans and in patients with clinical traits of a-v conduction disturbances requiring permanent pacing. The microscopic study was carried out on 30 normal human hearts specimens (17 F, 3 M) from 17 to 86 years of age, and on 20 hearts with conduction disturbances (11 F, 9 M) from 39 to 85 years of age. We found that the number of the atrioventricular node arteries is different and independent of the extent that induces block causing conduction disturbances. The topography of the artery in perinodal zone was consistent in normal hearts, yet in hearts with conduction disturbances we observed about 2% of deviations in its location. It might be the reason for generation of iatrogenic complications after invasive cardiological procedures. The morphology revealed changes in 50% of the examined hearts and their vessel walls, which was declared to be connected with ageing. This correlated with certain stages of atherosclerosis as well as hypertension characteristic of elderly patients. We observed that in 33% of hearts from control group small parietal thrombi were detected and in 60% of paced group respectively. Hence, it seems that the procedures in perinodal zone should be performed in its proximal part because of a minor probability of direct and indirect (through nodal artery) damage of the atrioventricular structure of the junction.

The morphological conditions of the permanent pacemaker lead extraction.

Pacemaker lead extraction is the treatment of choice in infectious complications regarding implantation procedure. The purpose of this study was to estimate the safety of the extraction in relation to the morphological changes of the pacing electrode. Research was carried out on materials consisting of 60 human hearts from 45 to 95 years of age (average 63 +/- 15 yrs), with VVI or DDD pacing (pacing duration 84 +/- 26 months) fixed in a formalin solution. Classical macroscopic anatomical methods were applied. In 44 hearts (73.3%) from the investigated group the posterior tricuspid leaflet was thickened only, and in 24 of these hearts the process regarded not only posterior leaflet but also the septal one and especially commissure between them. In 52 hearts (86.6%) inflammatory reaction spread also to the neighbouring part of the electrode. The length of the neointima-inflammatory tissue ranged from 4 to 8 mm (average 5 +/- 2 mm). On the tip of the electrode in the right ventricle cavity in 56 hearts (93.3%) we observed that endocardial leads were surrounded by fibrous thickening, and partially covered by endocardial tissue. We concluded that from the anatomical point of view the extraction of the pacing electrode seems to be questionable, especially in long-term permanent pacing. The experimental traction shows that only recently implanted electrodes were removed without any complications and in others with fraction of the tip, myocardial tissue avulsion or such removal was not successful at all.