Potassium Channel Blockade Enhances Atrial Fibrillation-Selective Antiarrhythmic Effects of Optimized State-Dependent Sodium Channel Blockade.
BACKGROUND
The development of effective and safe antiarrhythmic drugs for atrial fibrillation (AF) rhythm control is an unmet clinical need. Multichannel blockers are believed to have advantages over single-channel blockers for AF, but their development has been completely empirical to date. We tested the hypothesis that adding K(+)-channel blockade improves the atrium-selective electrophysiological profile and anti-AF effects of optimized Na(+)-channel blockers.


RESULTS
Realistic cardiomyocyte-, tissue-, and state-dependent Na(+)-channel block mathematical models, optical mapping, and action potential recording were used to study the effect of Na(+)-current (INa) blockade with or without concomitant inhibition of the rapid or ultrarapid delayed-rectifier K(+) currents (IKr and IKur, respectively). In the mathematical model, maximal AF selectivity was obtained with an inactivated-state Na(+)-channel blocker. Combining optimized Na(+)-channel blocker with IKr block increased rate-dependent and atrium-selective peak INa reduction, increased AF selectivity, and more effectively terminated AF compared with optimized Na(+)-channel blocker alone. Combining optimized Na(+)-channel blocker with IKur block had similar effects but without IKr block-induced ventricular action potential prolongation. Consistent with the mathematical model, in coronary-perfused canine hearts, the addition of dofetilide (selective IKr blocker) to pilsicainide (selective INa blocker) produced enhanced atrium-selective effects on maximal phase 0 upstroke and conduction velocity. Furthermore, pilsicainide plus dofetilide had higher AF termination efficacy than pilsicainide alone. Pilsicainide alone had no statistically significant effect on AF inducibility, whereas pilsicainide plus dofetilide rendered AF noninducible.


CONCLUSIONS
K(+)-channel block potentiates the AF-selective anti-AF effects obtainable with optimized Na(+)-channel blockade. Combining optimized Na(+)-channel block with blockade of atrial K(+) currents is a potentially valuable AF-selective antiarrhythmic drug strategy.
From the Research Center, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada (M.A., F.X., X.Y.Q., P.C., S.N.); Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering (M.A., P.C.) and Department of Medicine (S.N.), Université de Montréal, Montreal, QC, Canada; and Departments of Medicine (M.A., S.N.) and Pharmacology and Therapeutics (F.X., S.N.), McGill University, Montreal, QC, Canada; and West-German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (S.N.).
Martin
M
Aguilar
From the Research Center, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada (M.A., F.X., X.Y.Q., P.C., S.N.); Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering (M.A., P.C.) and Department of Medicine (S.N.), Université de Montréal, Montreal, QC, Canada; and Departments of Medicine (M.A., S.N.) and Pharmacology and Therapeutics (F.X., S.N.), McGill University, Montreal, QC, Canada; and West-German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (S.N.).
Feng
F
Xiong
From the Research Center, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada (M.A., F.X., X.Y.Q., P.C., S.N.); Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering (M.A., P.C.) and Department of Medicine (S.N.), Université de Montréal, Montreal, QC, Canada; and Departments of Medicine (M.A., S.N.) and Pharmacology and Therapeutics (F.X., S.N.), McGill University, Montreal, QC, Canada; and West-German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (S.N.).
Xiao Yan
XY
Qi
From the Research Center, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada (M.A., F.X., X.Y.Q., P.C., S.N.); Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering (M.A., P.C.) and Department of Medicine (S.N.), Université de Montréal, Montreal, QC, Canada; and Departments of Medicine (M.A., S.N.) and Pharmacology and Therapeutics (F.X., S.N.), McGill University, Montreal, QC, Canada; and West-German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (S.N.).
Philippe
P
Comtois
From the Research Center, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada (M.A., F.X., X.Y.Q., P.C., S.N.); Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering (M.A., P.C.) and Department of Medicine (S.N.), Université de Montréal, Montreal, QC, Canada; and Departments of Medicine (M.A., S.N.) and Pharmacology and Therapeutics (F.X., S.N.), McGill University, Montreal, QC, Canada; and West-German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (S.N.). stanley.nattel@icm-mhi.org.
Stanley
S
Nattel
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000503:physiopathology; D004285:Dogs; D026902:Potassium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use*; D026941:Sodium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use*
D000889:Anti-Arrhythmia Agents; D026902:Potassium Channel Blockers; D026941:Sodium Channel Blockers
anti-arrhythmia agents; atrial fibrillation