[E-C coupling of the failing myocardium]

Calcium ion (Ca2+) plays a central role in regulating E-C coupling in the heart. Intracellular Ca2+ homeostasis is maintained when all of subcellular steps for Ca2+ handling are functioning synchronously. Many investigators have proposed that the pathophysiologic basis for abnormal mechanical characteristics of the failing myocardium may be disturbed intracellular Ca2+ handlings, at one or more of the cellular sites. Recent advances of Ca2+ indicators have enabled to directly study the hypothesis in actively contracting myocardium. In acute contractile failure with ischemia or hypoxia, cellular sites or materials which block the normal E-C coupling have been mostly identified. For the mechanisms of abnormal contractions in the chronic failing myocardium, investigations are going on by using several experimental models and human hearts.