The vasodilatory effects of levosimendan on the human internal mammary artery

Levosimendan, an inotropic drug that enhances myocardial contractility through myofilment calcium sensitazion, induces peripheral vasodilation via opening ATP-dependent K(+) channels. It is unknown whether this drug can be used for the treatment of perioperative vasospasm of arterial conduits used for coronary artery bypass grafting.

We investigated the effects of levosimendan on human internal mammary artery (IMA) specimens taken from patients undergoing coronary artery bypass surgery. The rings were carefully prepared and placed between two wire hooks in organ bath chambers and then constricted submaximally with norepinephrine and thromboxane A(2) analog (U46619). Nitroglycerin, milrinone, and levosimendan were separately added in a cumulative fashion and concentration response curves for relaxation were constructed. In parallel experiments, the response to levosimendan was evaluated on rings with and without functional endothelium. Levosimendan prevention of norepinephrine-induced contraction was also estimated.

Nitroglycerin, milrinone, and levosimendan completely reversed the contraction of the IMA segments induced by U46619 and norepinephrine. Levosimendan produced a potent, concentration-dependent preventive effect on the norepinephrine-induced contraction of IMA. The responses to levosimendan were similar in preparations with or without endothelium.