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CARDIOVASCULAR ANESTHESIA

The Vasodilatory Effects of Levosimendan on the Human Internal Mammary Artery

Félix R. Montes, MD^*, Darío Echeverri, MD, Lorena Buitrago, MB, Isabel Ramírez, IE, Juan C. Giraldo, MD^*, Javier D. Maldonado, MD^||, and Juan P. Umaña, MD^||

From the Departments of *Anesthesiology, Cardiology, ||Cardiovascular Surgery, Laboratory of Vascular Function, Fundación CardioInfantil, Instituto de Cardiología; and Facultad de Ingeniería Industrial, Universidad de Los Andes, Bogota, Colombia, South America.

BACKGROUND: 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.

METHODS: 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 A₂ 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.

RESULTS: 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.