The Role of Ca++-sensitizers for the Treatment of Heart Failure

For increasing myocardial contractility in patients with cardiac failure, catecholamines, phosphodiesterase-III (PDE) inhibitors, and calcium sensitizers are available. Improving myocardial performance with catecholamines and PDE inhibitors leads to increased intracellular calcium concentration as an unavoidable side effect. An increase in intracellular calcium can induce harmful arrhythmias and increases the energetic demands of the myocardium. Long-term trials with PDE inhibitors have raised concerns about the safety of positive inotropic treatment for cardiac failure. Calcium sensitizers are a new class of inotropic drugs. They improve myocardial performance by directly acting on contractile proteins without increasing intracellular calcium load. Thus, they avoid the undesired effects of an increased intracellular calcium load. Calcium sensitizers may enhance myocardial performance without increasing myocardial oxygen consumption and without provoking fatal arrhythmias. Two calcium sensitizers are available for the treatment of cardiac failure in men. Pimobendan is a drug with positive inotropic effects that additionally inhibits the production of proinflammatory cytokines. However, it exerts a significant inhibition of PDE at clinically relevant doses. Levosimendan is a calcium sensitizer with no major inhibition of PDE at clinically relevant doses. It opens ATP-dependent potassium channels and thus has vasodilating and cardioprotective effects. The most important studies of the long-term treatment of stable cardiac failure with pimobendan and on the short-term treatment of unstable cardiac failure with levosimendan are presented.