HISTOLOGICAL EXAMINATION OF THE TOPOGRAPHY OF THE ATRIOVENTRICULAR NODAL ARTERY WITHIN THE TRIANGLE OF KOCH

The treatment of choice in patients with drug-resistant artioventricul ar nodal reentry tachycardia is radiofrequency fast or slow pathway ab lation. Ablation of the reentrant circuit in the region of the His bun dle, when approached from the anterior-superior region (fast pathway), can result in complete Ay block. This is less likely if the posterior -inferior (in the region of coronary sinus ostium) approach is used (s low pathway ablation). The possibility that radiofrequency energy may damage the vascular supply to the AV node must be considered. In order to confirm this hypothesis observation was conducted on the autopsy m aterial of 50 human hearts (20F, 30M) from 18 to 81 years of age. Spec imens were taken containing the triangle of Koch (the apex-right fibro us trigone, the base-coronary sinus ostium). These histological blocks were sectioned in the frontal plane and stained using Masson's method . Koch's triangle was divided in the sagittal plane into 3 parts: infe rior (between the base and the attachment of the tricuspid valve), cen tral (between the base and the apex of the right fibrous trigone) and superior (between this trigone and the tendon of Todaro). It was obser ved that the AVN artery at the coronary sinus ostium level (the base o f the triangle of Koch) was positioned in 68% in the central and in 32 % in the inferior part of Koch's triangle. The AVN artery in the centr al part was removed from the endocardium 1mm (18%), 2mm (42%), 3mm (22 %), 4mm (18%). In the inferior part 1mm (26%), 2mm (37%), 3mm (37%). N o statistically significant relationship was observed between those gr oups Conclusions: I) in 20% of examined hearts the AVN artery lay just beneath the endocardium near the coronary sinus ostium 2) there is a risk of the AVN artery coagulation during radiofrequency ablation in t he slow pathway region.