Congestive heart failure (CHF) is a chronic medical condition whoseincidence is rising. The prevalence of CHF is approximately 1% to3% in Western countries. Despite innovations in medical therapy,CHF is associated with high morbidity and mortality rates.

CHF patients commonly experience muscle weakness and fatigueas two major symptoms. An altered intracellular handling ofionized calcium has been suggested to play a vital role in impairedmyocardial contraction. In isolated myocytes from patientswith end stage heart failure, systolic ionized calcium levelswere markedly decreased, while diastolic levels were elevated ascompared to healthy controls. In addition, digitalis and betablockermedical therapy is frequently used in CHF patients andis known to increase myocardial ionized calcium levels.