Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis

Area of Science:

• Cardiovascular morphology
• Cardiac electrophysiology
• Histology

Background:

• The structure of the atrioventricular (AV) conduction system, specifically the non-branching bundle of specialized cardiomyocytes, is debated.
• Understanding these interconnections is crucial for comprehending cardiac electrical activity.

Purpose of the Study:

• To investigate the presence or absence of interconnections between specialized cardiomyocytes in the non-branching bundle of the AV conduction axis.
• To clarify the controversial topic of longitudinal dissociation within this cardiac structure.

Main Methods:

• Morphological analysis using three-dimensional assessment in human, canine, and bovine hearts.
• Examination of longitudinal and orthogonal serial histological sections.
• Assessment of India ink injected specimens for 3D arrangement of cardiomyocytes.

Main Results:

• Numerous oblique interconnections were observed between specialized cardiomyocyte groups in longitudinal sections.
• Orthogonal sections revealed significant variation in cardiomyocyte grouping, suggesting bifurcation and convergence.
• Three-dimensional assessment confirmed extensive interconnections within the non-branching bundle.

Conclusions:

• The presence of multiple interconnections between cardiomyocytes in the non-branching bundle refutes the possibility of longitudinal dissociation.
• This study provides definitive morphological evidence clarifying the structural organization of the AV conduction axis.