Fluorescent imaging of a dual-pathway atrioventricular-nodal conduction system

A dual-pathway theory to explain atrioventricular-nodal (AVN) reentry has b een proposed previously. However, the exact anatomical and functional corre lates of the fast pathway (FP) and slow pathway (SP) have not yet been eluc idated. We used optical mapping to reconstruct patterns of activation durin g retrograde conduction through the AVN and during AVN reentry in the trian gles of Koch of 12 rabbits, Reentry was inducible by a premature stimulatio n of the bundle of His in 6 preparations (50%), A functional FP and SP appe ar to be anatomically correlated with posterior and posterolateral extensio ns of the AVN, which were recently described. Retrograde breakthrough point s in 6 noninducible preparations were clustered near the apex of the triang le of Koch (FP), whereas 6 inducible preparations had either cycle length-d ependent FP and SP exits (n=3) or only SP exits located near the coronary s inus orifice. The shift of breakthrough points from FP to SP during progres sive shortening of the coupling interval was accompanied by a discontinuity in the conduction curve. We observed a transmural reentrant circuit involv ing the AVN, FP, SP, and the superficial endocardial layer of atrial and tr ansitional cells. The presence of a functional SP during retrograde conduct ion was associated with inducibility of AVN reentry. The full text of this article is available at http://www.circresaha.org.