The effects of levosimendan on myocardial oxygen consumption and coronary blood flow early after coronary artery bypass grafting

Levosimendan (LS) is a myocardial calcium sensitiser indicated for the treatment of acute decompensated heart failure. This randomised, double-blind trial evaluated the haemodynamic effects of LS in low-risk patients (n = 23) following coronary artery bypass surgery. The effects of LS on myocardial oxygen (O₂) consumption, coronary blood flow and systemic haemodynamics were measured by thermodilution. Patients received LS, 8 μg/kg (n = 8), or LS, 24 μg/kg (n = 7), or placebo (n = 8) as a 5-min infusion 1 hour after surgery. Measurements of systemic and coronary sinus haemodynamics, myocardial O₂ consumption and cardiac substrate utilisation were made, before and after treatment with LS.

Levosimendan, 8 μg/kg and 24 μg/kg, significantly increased cardiac output (CO) by 0.7 and 1.6 l/min, respectively (P < 0.05), compared to baseline. Mean arterial pressure and pulmonary vascular resistance decreased significantly with both doses of LS, as did coronary artery resistance, the latter being indicative of coronary vasodilation (P < 0.05). Furthermore, an increase in coronary blood flow of 28 ml/min and 42 ml/min with LS, 8 μg/kg and 24 μg/kg, respectively, was obtained (P = 0.054 for both doses combined). Despite the markedly improved cardiac function seen with LS, neither dose significantly increased myocardial O₂ consumption compared with placebo. In addition, no significant differences in myocardial free fatty acid, lactate, pyruvate and glucose utilisation were observed in LS-treated patients compared to placebo controls.

In conclusion, based on the results of this study, LS may be of significant benefit in improving cardiac function in patients with low CO following coronary artery bypass surgery, with no significant increase in O₂ consumption.