For persons suffering from New York Heart Association (NYHA) class II chronic heart failure with left ventricular systolic dysfunction (with ejection fraction less than or equal to 35 percent), as a complement to standard therapy. Note: Patients must be on optimal therapy with an angiotensin-converting-enzyme (ACE) inhibitor, an angiotensin-receptor blocker (ARB), or both and a beta-blocker (unless contraindicated) at the recommended dose or maximal tolerated dose.