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Structure/function of the supraventricular pacemaking & conduction system of the rabbit heart
Author(s) -
Efimov Igor R,
Hucker William,
Fedorov Vadim V,
Dobrzynski Halina
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1301-d
Subject(s) - cardiology , rabbit (cipher) , electrical conduction system of the heart , function (biology) , supraventricular arrhythmia , medicine , anatomy , electrocardiography , biology , microbiology and biotechnology , mathematics , atrial fibrillation , statistics
In contrast to the ventricular domain of the pacemaking and conduction system, the supraventricular system remains hotly debated. We used optical mapping, optical coherence tomography (OCT), and quantitative confocal immunofluorescence in order to map its structure/function in the rabbit heart. Functional studies reveal that this region extends from superior to inferior vena cavas, around the coronary sinus and merged with the AV node. This system has pacemaking properties, slow conduction velocity, and is under strong autonomic control. OCT revealed a highly complex fibrous structure of this region, which is distinctly different from the organized parallel fibers of the neighboring crista terminalis, and a septal block zone lacking myocytes. Immunohistochemistry revealed that myocytes of this region express neurofilament 160 and do not express connexin 43 or connexin 40, which is opposite to myocytes from atrial myocardium. Immunostaining of TH and ChAT demonstrated 4‐fold higher density of sympathetic and parasympathetic innervation in this region as compared to atrial myocardium. Moreover, density of autonomic innervation is arranged in a superior‐inferior gradient, which is consistent with vagally induced shift of pacemaker, observed using optical mapping. Conclusions Combined functional, structural and molecular mapping of the rabbit right atrium revealed a continuous functional pacemaking and slowly conducting domain, which is distinctly different from neighboring atrial myocardium. We suggest that this region is defined as the supraventricular domain of a unified cardiac pacemaking and conduction system of the heart. Supported by NIH grant HL58808