Affiliation:
1. From the Laboratory of Experimental Cardiology, Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands (B.O.B., Z.N., S.F.A.A., D.L.Y., M.J.S., A.A.V.d.V., D.A.P.); and Department of Physics and Astronomy, Ghent University, Ghent, Belgium (I.V.K., A.V.P.).
Abstract
Background—
Atrial fibrillation is the most common cardiac arrhythmia. Ventricular proarrhythmia hinders pharmacological atrial fibrillation treatment. Modulation of atrium-specific Kir3.x channels, which generate a constitutively active current (
I
K,ACh-c
) after atrial remodeling, might circumvent this problem. However, it is unknown whether and how
I
K,ACh-c
contributes to atrial fibrillation induction, dynamics, and termination. Therefore, we investigated the effects of
I
K,ACh-c
blockade and Kir3.x downregulation on atrial fibrillation.
Methods and Results—
Neonatal rat atrial cardiomyocyte cultures and intact atria were burst paced to induce reentry. To study the effects of Kir3.x on action potential characteristics and propagation patterns, cultures were treated with tertiapin or transduced with lentiviral vectors encoding
Kcnj3
- or
Kcnj5
-specific shRNAs. Kir3.1 and Kir3.4 were expressed in atrial but not in ventricular cardiomyocyte cultures. Tertiapin prolonged action potential duration (APD; 54.7±24.0 to 128.8±16.9 milliseconds;
P
<0.0001) in atrial cultures during reentry, indicating the presence of
I
K,ACh-c
. Furthermore, tertiapin decreased rotor frequency (14.4±7.4 to 6.6±2.0 Hz;
P
<0.05) and complexity (6.6±7.7 to 0.6±0.8 phase singularities;
P
<0.0001). Knockdown of
Kcnj3
or
Kcnj5
gave similar results. Blockade of
I
K,ACh-c
prevented/terminated reentry by prolonging APD and changing APD and conduction velocity restitution slopes, thereby altering the probability of APD alternans and rotor destabilization. Whole-heart mapping experiments confirmed key findings (eg, >50% reduction in atrial fibrillation inducibility after
I
K,ACh-c
blockade).
Conclusions—
Atrium-specific Kir3.x controls the induction, dynamics, and termination of fibrillation by modulating APD and APD/conduction velocity restitution slopes in atrial tissue with
I
K,ACh-c
. This study provides new molecular and mechanistic insights into atrial tachyarrhythmias and identifies Kir3.x as a promising atrium-specific target for antiarrhythmic strategies.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Cited by
31 articles.
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