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Figure 2. Direct 3-dimensional analysis of AV
junction region in selected serial orthogonal sections. A and B,
Vertical lines indicate section level in C. B, C1, Coronary
sinus ostium (CSO) and black dot identify a regularly appearing sinus
in lateral, inferoanterior lip of coronary sinus ostium. A,
Parallel plane: the PAVB, AVN, and DAVB span AV junction region as a
myocardial continuum confluent with right bundle-branch (RBB); medial
atrionodal bundle (MAB) and lateral atrionodal bundle (LAB) are located
on either side of coronary sinus (CS); and superior atrionodal
bundle (SAB) is superior to AVN. Dashed lines, Kochs triangle. B,
Perpendicular plane: collagen encasement imparts a gray tone to PAVB, AVN, and DAVB
in contrast to dark staining of medial atrial wall (MAW) and
ventricular septum (VS) myocardium. White
arrowheads delineate MAW annular, subepicardial circumferential lamina.
Thin sleeve of central fibrous body connective tissue separates AVN
from MAW. C, Transverse plane. C1, MAB and LAB converge. C2, Collagen
septa separate vertical stack of PAVB fascicles atop VS. C3,
Convergence of SAB and PAVB. C4, SAB is superior to AVN, which is
surrounded by halo of central fibrous body connective tissue.
Perpendicular lamina myofibers cascade over central fibrous body and
descend into medial leaflet. C5, DAVB within central fibrous body and
astride VS. Note specialized tissues are outside MAW. C1, CSFo and star
indicate CS fossa; LA, left atrium; n, noncoronary posterior
aortic valve sinus wall; TT, tendon of Todaro. Calibration bar in A and
B, C1. (Goldners trichrome.)
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