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Editorial |
From the Laboratory of Pharmacology and Toxicology (S.A.-A.), Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan, and Department of Pharmacology II (Y.K.), Graduate School of Medicine, Osaka University, Osaka, Japan.
Correspondence to Yoshihisa Kurachi, MD, PhD, Department of Pharmacology II, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan. E-mail ykurachi@pharma2.med.osaka-u.ac.jp
Key Words: heart failure arrhythmogenesis Na+-Ca2+ exchanger inwardly rectifying K+ channels ß-adrenergic receptor
Heart failure is a multifactorial syndrome of hemodynamic decompensation that is a final common pathway for a variety of cardiovascular disorders. More than 40% of patients with heart failure lose their lives because of sudden cardiac death. Thus, the prevention of life-threatening cardiac arrhythmia is one of the major goals in the treatment of heart failure. The Cardiac Arrhythmia Suppression Trial (CAST) study has shown that class I antiarrhythmic agents are not clinically beneficial for long-term treatment of arrhythmias in patients with previous myocardial infarction. Although ß-adrenergic blockers and amiodarone are effective in reducing arrhythmic mortality,1 the underlying mechanisms are not fully understood. Thus, development of the experimental animal models and comprehensive studies for elucidation of pathophysiological characteristics of life-threatening cardiac arrhythmias in heart failure is of fundamental importance.
The electrophysiological
substrates associated with life-threatening cardiac arrhythmias
are varied and include impairment of conduction attributable to
structural alterations, spatial and temporal inhomogeneity of action
potential duration attributable to remodeling of ionic channels, and
triggered activity.2 There
are several studies describing changes in the functional expression of
various ion channels and Ca2+-handling
proteins/systems in cardiac myocytes isolated from failing
hearts.3 4 In human
and some animal models of heart failure, the protein level of the
sarcoplasmic reticulum (SR) Ca2+ ATPase
(SERCA) is reduced and that of
Na+-Ca2+
exchanger (NCX) is
increased.4 It has also been
reported that the reduced SR Ca2+ uptake
activity and enhanced Ca2+ extrusion via NCX
results in a decrease of the Ca2+ content in
the SR
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