Electrophysiological mechanisms of ventricular arrhythmias in relation to Andersen-Tawil syndrome under conditions of reduced I K1: A simulation study

Ruey J. Sung, Sheng-Nan Wu, Jiun Shian Wu, Han Dong Chang, Ching Hsing Luo

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Abstract

Patients with Andersen-Tawil syndrome (ATS) mostly have mutations on the KCNJ2 gene, producing loss of function or dominant-negative suppression of the inward rectifier K + channel Kir2.1. However, clinical manifestations of ATS including dysmorphic features, periodic paralysis (hypo-, hyper-, or normokalemic), long QT, and ventricular arrhythmias (VAs) are considerably variable. Using a modified dynamic Luo-Rudy simulation model of cardiac ventricular myocytes, we attempted to elucidate mechanisms of VA in ATS by analyzing effects of the inward rectifier K + channel current (I K1 ) on the action potential (AP). During pacing at 1.0 Hz with extracellular K + concentration ([K + ] o ) at 4.5 mM, a stepwise 10% reduction of Kir2.1 channel conductance progressively prolonged the terminal repolarization phase of the AP along with gradual depolarization of the resting membrane potential (RMP). At 90% reduction, early afterdepolarizations (EADs) became inducible and RMP was depolarized to -52.0 mV (control: -89.8 mV), followed by emergence of spontaneous APs. Both EADs and spontaneous APs were facilitated by a decrease in [K + ] o and suppressed by an increase in [K + ] o . Simulated β-adrenergic stimulation enhanced delayed afterdepolarizations (DADs) and could also facilitate EADs as well as spontaneous APs in the setting of low [K + ] o and reduced Kir2.1 channel conductance. In conclusion, the spectrum of VAs in ATS may include 1) triggered activity mediated by EADs and/or DADs and 2) abnormal automaticity manifested as spontaneous APs. These VAs can be aggravated by a decrease in [K + ] o and β-adrenergic stimulation and may potentially induce torsade de pointes and cause sudden death. In patients with ATS, the hypokalemic form of periodic paralysis should have the highest propensity to VAs, especially during physical activity.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume291
Issue number6
DOIs
Publication statusPublished - 2006 Dec 18

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Andersen Syndrome
Cardiac Arrhythmias
Inwardly Rectifying Potassium Channel
Adrenergic Agents
Membrane Potentials
Action Potentials
Familial Periodic Paralysis
Hyperkalemic Periodic Paralysis
Hypokalemic Periodic Paralysis
Torsades de Pointes
Sudden Death
Cardiac Myocytes
Cause of Death
Exercise
Mutation
Genes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Cite this

@article{77d0b0fc491a4290a2b35a1362c88063,
title = "Electrophysiological mechanisms of ventricular arrhythmias in relation to Andersen-Tawil syndrome under conditions of reduced I K1: A simulation study",
abstract = "Patients with Andersen-Tawil syndrome (ATS) mostly have mutations on the KCNJ2 gene, producing loss of function or dominant-negative suppression of the inward rectifier K + channel Kir2.1. However, clinical manifestations of ATS including dysmorphic features, periodic paralysis (hypo-, hyper-, or normokalemic), long QT, and ventricular arrhythmias (VAs) are considerably variable. Using a modified dynamic Luo-Rudy simulation model of cardiac ventricular myocytes, we attempted to elucidate mechanisms of VA in ATS by analyzing effects of the inward rectifier K + channel current (I K1 ) on the action potential (AP). During pacing at 1.0 Hz with extracellular K + concentration ([K + ] o ) at 4.5 mM, a stepwise 10{\%} reduction of Kir2.1 channel conductance progressively prolonged the terminal repolarization phase of the AP along with gradual depolarization of the resting membrane potential (RMP). At 90{\%} reduction, early afterdepolarizations (EADs) became inducible and RMP was depolarized to -52.0 mV (control: -89.8 mV), followed by emergence of spontaneous APs. Both EADs and spontaneous APs were facilitated by a decrease in [K + ] o and suppressed by an increase in [K + ] o . Simulated β-adrenergic stimulation enhanced delayed afterdepolarizations (DADs) and could also facilitate EADs as well as spontaneous APs in the setting of low [K + ] o and reduced Kir2.1 channel conductance. In conclusion, the spectrum of VAs in ATS may include 1) triggered activity mediated by EADs and/or DADs and 2) abnormal automaticity manifested as spontaneous APs. These VAs can be aggravated by a decrease in [K + ] o and β-adrenergic stimulation and may potentially induce torsade de pointes and cause sudden death. In patients with ATS, the hypokalemic form of periodic paralysis should have the highest propensity to VAs, especially during physical activity.",
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Electrophysiological mechanisms of ventricular arrhythmias in relation to Andersen-Tawil syndrome under conditions of reduced I K1 : A simulation study. / Sung, Ruey J.; Wu, Sheng-Nan; Wu, Jiun Shian; Chang, Han Dong; Luo, Ching Hsing.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 291, No. 6, 18.12.2006.

Research output: Contribution to journalArticle

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T1 - Electrophysiological mechanisms of ventricular arrhythmias in relation to Andersen-Tawil syndrome under conditions of reduced I K1

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AU - Sung, Ruey J.

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