CARDIOVASCULAR
ENGINEERING

Official Publication of the World Artificial Organ, Immunology and Transplantation Society (WAITS)

Volume 10, 2005, No 1

Distribution of the AV Nodal Tissue in Both Atria: With Reference to its Arrhythmogenisity
S. Inoue, T. Matsuyama, G. Ogawa, M. Tokunoh, Y. Kobayashi, F. Yoshida, H. Ota, T. Katagiri

The reentrant circuit of the atrioventricular nodal reentrant tachycardia (AVNRT) remains as yet not fully understood. Recently prevalence of slow pathway ablation in front of the coronary sinus opening as optimal target revealed crucial role of this area in reentry circuit. The fact that AVNRT is rare in infants could indicate that aging remodeling of the AV septal junction is involved. To evaluate the potential role of the anatomical alternation with aging, we have reconstructed the musculature of the lower AV septal junctional area in human hearts. In 28 human hearts obtained at autopsy, the area containing Koch's triangle was excised and serially sectioned at 10?m thickness. Ages ranged from 3 months to 81 years (6 hearts under 16 year; 11 hearts between 32 and 59 years; 11 hearts over 60 years). Two cases over 60 years experienced AVNRT but all other hearts did not show obvious arrhythmia.
Results: In infants under 2 years of age, the AV septal junction fully consisted of myocardium with very little interstitial fibro-fatty tissue. The transitional layer adhered continuously to the whole AV nodal axis beneath the atrial myocardium. In infants over 3 years of age already fatty infiltration was encountered around nodal tissues, which resulted in loosening of the contacts between the transitional layer and the nodal tissue. In 11 adult hearts below 60 years of age, the transitional layer gradually diminished and became more and more replaced by fibro-fatty tissue. In 3 hearts in this group, the transitional layers appeared partially interrupted in their nodal contacts, while the residual parts only connected the right and left atrial myocardium beneath the coronary sinus musculature. In 9 control hearts over 60 years of age only 3 cases showed a distinct transitional cell layer. Contrary to the age-related changes within the transitional layer, the nodal tissues including inferior extensions were hardly affected by aging. In two AVNRT cases atrionodal connection in rightward extension was deviated to left atrium through diffuse transitional layer leaving nodal tissue isolated from right atrial musculature.
Conclusions: Aging of the heart resulted in an increase in the fibro-fatty tissue within inferior septal junction, and hence divers discontinuity in atrionodal connection. In AVNRT patients, leftward deviation of atrionodal connection on rightward nodal extension seems to arrange the nodal reentry.

(CVE. 2005; 10 (1): 43-46)

Key words: atrioventricular node, AVNRT, slow pathway, dual AV node physiology, jump-up phenomenon, catheter ablation, inferior extension

Shin Inoue
4-1-18 Toyosu
Koto-ku
135-8577 Tokyo
Japan
E-mail: inoues@med.showa-u.ac.jp