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2017 ; 9
(400
): ä Nephropedia Template TP
gab.com Text
Twit Text FOAVip
Twit Text #
English Wikipedia
Redundant and diverse intranodal pacemakers and conduction pathways protect the
human sinoatrial node from failure
#MMPMID28747516
Li N
; Hansen BJ
; Csepe TA
; Zhao J
; Ignozzi AJ
; Sul LV
; Zakharkin SO
; Kalyanasundaram A
; Davis JP
; Biesiadecki BJ
; Kilic A
; Janssen PML
; Mohler PJ
; Weiss R
; Hummel JD
; Fedorov VV
Sci Transl Med
2017[Jul]; 9
(400
): ä PMID28747516
show ga
The human sinoatrial node (SAN) efficiently maintains heart rhythm even under
adverse conditions. However, the specific mechanisms involved in the human SAN's
ability to prevent rhythm failure, also referred to as its robustness, are
unknown. Challenges exist because the three-dimensional (3D) intramural structure
of the human SAN differs from well-studied animal models, and clinical electrode
recordings are limited to only surface atrial activation. Hence, to innovate the
translational study of human SAN structural and functional robustness, we
integrated intramural optical mapping, 3D histology reconstruction, and molecular
mapping of the ex vivo human heart. When challenged with adenosine or atrial
pacing, redundant intranodal pacemakers within the human SAN maintained
automaticity and delivered electrical impulses to the atria through sinoatrial
conduction pathways (SACPs), thereby ensuring a fail-safe mechanism for robust
maintenance of sinus rhythm. During adenosine perturbation, the primary central
SAN pacemaker was suppressed, whereas previously inactive superior or inferior
intranodal pacemakers took over automaticity maintenance. Sinus rhythm was also
rescued by activation of another SACP when the preferential SACP was suppressed,
suggesting two independent fail-safe mechanisms for automaticity and conduction.
The fail-safe mechanism in response to adenosine challenge is orchestrated by
heterogeneous differences in adenosine A1 receptors and downstream GIRK4 channel
protein expressions across the SAN complex. Only failure of all pacemakers and/or
SACPs resulted in SAN arrest or conduction block. Our results unmasked reserve
mechanisms that protect the human SAN pacemaker and conduction complex from
rhythm failure, which may contribute to treatment of SAN arrhythmias.
|Action Potentials/drug effects
[MESH]
|Adenosine/pharmacology
[MESH]
|Adult
[MESH]
|Aged
[MESH]
|Arrhythmias, Cardiac/metabolism/*physiopathology/prevention & control
[MESH]