Левосимендан

Levosimendan was introduced in Sweden as an i.v. infusion for the treatment of acute heart failure or refractory symptoms of chronic heart failure in cases where conventional treatment (e.g., diuretic or ACE inhibitor) is not sufficient. Levosimendan is the (R)- enantiomer of simendan that belongs to the same class as pimobendan (Boehringer Ingelheim).

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Levosimendan is a positive inotropic agent that acts by sensitising troponin C to Ca2+, prolonging actin-myosin cross-bridge formation and therefore increasing contractility. This is an energy-independent process and therefore does not increase myocardial oxygen demand. Levosimendan also causes vasodilatation by opening ATP-sensitive K+ channels in vascular smooth muscle, reducing pre- and afterload and improving myocardial oxygen supply. It may have a role in the management of acute heart failure and postresuscitation myocardial dysfunction.

Levosimendan is a calcium sensitizer that can cause increased cardiac contractility by binding troponin C (EC50 = 9 nM), promotes vasodilation by activating ATP-sensitive potassium channels on vascular smooth muscle cells (EC50 = 0.28 μM), and performs a cardioprotective function by prompting the opening of mitochondrial potassium channels in cardiomyocytes. It also has been reported to inhibit phosphodiesterases 3 and 4 in left ventricular cardiac tissue with IC50 values of 2.5 nM and 25 μM, respectively.

Levosimendan is an innovative myofilament calcium sensitizer that increases myocardial contractility by selectively binding to the N-terminus of troponin C and by stabilizing the Ca2+-bound conformation of this contractile protein. It also activates ventricular and arterial adenostne triphosphate-regulated potassium channels which causes vasodilatation in vascular smooth muscle and protects myocardium against infarction. Its low phosphodiesterase III inhibiting activity is probably not responsible for its positive inotropic, lusitropic and dilating effects. Unlike other cardiotonic drugs, levosimendan is able to produce positive inotropic effects without prolonging myocardial relaxation or increasing the incidence of malignant arrythmias. It was clinically shown to have a lower risk of mortality in patients with heart failure when compared to placebo and dobutamine. Since it has a larger potential, levosimendan is currently under further clinical evaluation as a chronic treatment for congestive heart failure.