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Editorial
. 2020 Dec;6(14):1841-1843.
doi: 10.1016/j.jacep.2020.09.017. Epub 2020 Nov 25.

The Sinus Node: Still Mysterious After All These Years

James N Weiss  1 , Zhilin Qu  2
Affiliations
Editorial

The Sinus Node: Still Mysterious After All These Years

James N Weiss et al. JACC Clin Electrophysiol. 2020 Dec.
No abstract available

Keywords: autonomic tone; ca clock; membrane clock; pacemaking; sino-atrial node.

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Conflict of interest statement

Author Disclosures Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Figures

FIGURE 1
FIGURE 1. Two Coupled Clocks in Pacemaking SAN Cells
(A) Schematic of the 2 clocks, a membrane clock (M-clock) utilizing ion channels (such as HCN4 channels comprising 1f) in the sarcolemmal membrane to trigger the action potential (AP), and a Ca-clock utilizing intracellular Ca cycling between the sarcoplasmic reticulum and cytoplasm coupled to the sarcolemmal inward Na-Ca exchange current (INaCa) to trigger the AP. (B) The M-clock mechanism can be modeled deterministically as a limit cycle oscillator with a limited dynamic range that maintains a stable minimum heart rate and avoids severe bradycardia when vagal tone increases (green line). The Ca-clock mechanism can be modeled as criticality, whose power law features provide a wide dynamic range of heart rate to accelerate the heart rate dramatically when sympathetic tone increases (blue line). With both mechanisms together, the heart rate follows the red line as autonomic tone changes. Note that the red line is higher than both the green and blue lines, reflecting the synergistic interaction between the 2 coupled clocks.
See this image and copyright information in PMC

Comment on

References

    1. Brennan JA, Chen Q, Gams A, et al. Evidence of superior and inferior sinoatrial nodes in the mammalian heart. J Am Coll Cardiol EP 2020;6:1827–40. - PMC - PubMed
    1. Lyashkov AE, Behar J, Lakatta EG, Yaniv Y, Maltsev VA. Positive feedback mechanisms among local Ca Releases, NCX, and ICaL ignite pacemaker action potentials. Biophys J 2018;114:2024. - PMC - PubMed
    1. Joung B, Tang L, Maruyama M, et al. Intracellular calcium dynamics and acceleration of sinus rhythm by beta-adrenergic stimulation. Circulation 2009;119:788–96. - PMC - PubMed
    1. Efimov IR, Fedorov VV, Joung B, Lin SF. Mapping cardiac pacemaker circuits: methodological puzzles of the sinoatrial node optical mapping. Circ Res 2010;106:255–71. - PMC - PubMed
    1. Nivala M, Ko CY, Nivala M, Weiss JN, Qu Z. Criticality in intracellular calcium signaling in cardiac myocytes. Biophys J 2012;102:2433–42. - PMC - PubMed

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