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(Circulation Research. 2008;102:975.)
© 2008 American Heart Association, Inc.

Integrative Physiology

Computer Three-Dimensional Reconstruction of the Atrioventricular Node

Jue Li^*, Ian D. Greener^*, Shin Inada, Vladimir P. Nikolski, Mitsuru Yamamoto, Jules C. Hancox, Henggui Zhang, Rudi Billeter, Igor R. Efimov, Halina Dobrzynski^**, Mark R. Boyett^**

From the Cardiovascular Research Group, Faculty of Medical and Human Sciences (J.L., I.D.G., S.I., H.D., M.R.B.), Biological Physics Group, School of Physics and Astronomy (H.Z.), University of Manchester, UK; Washington University (V.P.N., I.R.E.), St Louis, Mo; Nagoya University (M.Y.), Japan; University of Bristol (J.C.H.), UK; and University of Nottingham (R.B.), UK.

Correspondence to Prof M.R. Boyett, Cardiovascular Research Group, Faculty of Medical and Human Sciences, University of Manchester, Core Technology Facility, 46 Grafton St, Manchester M13 9NT, United Kingdom. E-mail mark.boyett{at}manchester.ac.uk

Because of its complexity, the atrioventricular node (AVN), remains 1 of the least understood regions of the heart. The aim of the study was to construct a detailed anatomic model of the AVN and relate it to AVN function. The electric activity of a rabbit AVN preparation was imaged using voltage-dependent dye. The preparation was then fixed and sectioned. Sixty-five sections at 60- to 340-µm intervals were stained for histology and immunolabeled for neurofilament (marker of nodal tissue) and connexin43 (gap junction protein). This revealed multiple structures within and around the AVN, including transitional tissue, inferior nodal extension, penetrating bundle, His bundle, atrial and ventricular muscle, central fibrous body, tendon of Todaro, and valves. A 3D anatomically detailed mathematical model (13 million element array) of the AVN and surrounding atrium and ventricle, incorporating all cell types, was constructed. Comparison of the model with electric activity recorded in experiments suggests that the inferior nodal extension forms the slow pathway, whereas the transitional tissue forms the fast pathway into the AVN. In addition, it suggests the pacemaker activity of the atrioventricular junction originates in the inferior nodal extension. Computer simulation of the propagation of the action potential through the anatomic model shows how, because of the complex structure of the AVN, reentry (slow–fast and fast–slow) can occur. In summary, a mathematical model of the anatomy of the AVN has been generated that allows AVN conduction to be explored.

Key Words: atrioventricular node • slow pathway • fast pathway • reentry • modeling