TY - JOUR
T1 - Structural and functional evidence for discrete exit pathways that connect the canine sinoatrial node and atria
AU - Fedorov, Vadim V.
AU - Schuessler, Richard B.
AU - Hemphill, Matthew
AU - Ambrosi, Christina M.
AU - Chang, Roger
AU - Voloshina, Alexandra S.
AU - Brown, Kathy
AU - Hucker, William J.
AU - Efimov, Igor R.
PY - 2009/4/10
Y1 - 2009/4/10
N2 - Surface electrode recordings cannot delineate the activation within the human or canine sinoatrial node (SAN) because they are intramural structures. Thus, the site of origin of excitation and conduction pathway(s) within the SAN of these mammals remains unknown. Canine right atrial preparations (n=7) were optically mapped. The SAN 3D structure and protein expression were mapped using immunohistochemistry. SAN optical action potentials had diastolic depolarization and multiple upstroke components that corresponded to the separate excitations of the node and surface atrial layers. Pacing-induced SAN exit block eliminated atrial optical action potential components but retained SAN optical action potential components. Excitation originated in the SAN (cycle length, 557±72 ms) and slowly spread (1.2 to 14 cm/sec) within the SAN, failing to directly excite the crista terminalis and intraatrial septum. After a 49±22 ms conduction delay within the SAN, excitation reached the atrial myocardium via superior and/or inferior sinoatrial exit pathways 8.8±3.2 mm from the leading pacemaker site. The ellipsoidal 13.7±2.8/4. 9±0.6 mm SAN structure was functionally insulated from the atrium. This insulation coincided with connexin43-negative regions at the borders of the node, connective tissue, and coronary arteries. During normal sinus rhythm, the canine SAN is functionally insulated from the surrounding atrial myocardium except for 2 (or more) narrow superior and inferior sinoatrial exit pathways separated by 12.8±4.1 mm. Conduction failure in these sinoatrial exit pathways leads to SAN exit block and is a modulator of heart rate.
AB - Surface electrode recordings cannot delineate the activation within the human or canine sinoatrial node (SAN) because they are intramural structures. Thus, the site of origin of excitation and conduction pathway(s) within the SAN of these mammals remains unknown. Canine right atrial preparations (n=7) were optically mapped. The SAN 3D structure and protein expression were mapped using immunohistochemistry. SAN optical action potentials had diastolic depolarization and multiple upstroke components that corresponded to the separate excitations of the node and surface atrial layers. Pacing-induced SAN exit block eliminated atrial optical action potential components but retained SAN optical action potential components. Excitation originated in the SAN (cycle length, 557±72 ms) and slowly spread (1.2 to 14 cm/sec) within the SAN, failing to directly excite the crista terminalis and intraatrial septum. After a 49±22 ms conduction delay within the SAN, excitation reached the atrial myocardium via superior and/or inferior sinoatrial exit pathways 8.8±3.2 mm from the leading pacemaker site. The ellipsoidal 13.7±2.8/4. 9±0.6 mm SAN structure was functionally insulated from the atrium. This insulation coincided with connexin43-negative regions at the borders of the node, connective tissue, and coronary arteries. During normal sinus rhythm, the canine SAN is functionally insulated from the surrounding atrial myocardium except for 2 (or more) narrow superior and inferior sinoatrial exit pathways separated by 12.8±4.1 mm. Conduction failure in these sinoatrial exit pathways leads to SAN exit block and is a modulator of heart rate.
KW - Connexin43
KW - Optical mapping
KW - Sinoatrial exit block
KW - Sinoatrial node
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U2 - 10.1161/CIRCRESAHA.108.193193
DO - 10.1161/CIRCRESAHA.108.193193
M3 - Article
C2 - 19246679
AN - SCOPUS:65249100262
SN - 0009-7330
VL - 104
SP - 915
EP - 923
JO - Circulation research
JF - Circulation research
IS - 7
ER -