BACKGROUND. In chronic heart failure (CHF) beta-blockers reduce myocardial oxygen consumption and improve myocardial efficiency by shifting myocardial substrate utilization from increased free fatty acid oxidation to increased glucose oxidation. The effect of selective and non-selective beta-blockers on total body resting energy production rate (EPR) and substrate utilization is not known. METHODS. Twenty-six non-cachectic patients with moderately severe heart failure (NYHA class II or III, left ventricular ejection fraction