Heart failure patients (left ventricular ejection fraction (LVEF ≤ 40%) are randomized to receive tablets of 300mg or placebo for 1 months in a double-blind fashion. All subjects will be on stable optimal medical therapy according to the present guidelines for at least 3 months before enrolment. At randomization and at study end, echocardiography by a single observer will be performed and assessment of symptoms and signs and quality of life based on self scoring system (from 1 to 7) and objective physical examinations will be done.