Inclusion Criteria:

• Greater than or equal to 18 years of age
• NYHA class III or IV CHF
• Females must not be pregnant or lactating. Females of childbearing potential and males must use a reliable means of contraception
• Serum total T3 <= 95 ng/dL with normal levels of TSH
• On a regimen consisting of angiotensin-converting enzyme inhibitors and/or angiotensin receptor antagonists, beta blockers, and diuretics for a minimum of 3 months prior to randomization
• Clinically stable for 2 weeks prior to randomization (defined as no change in functional class by NYHA, no hospitalization or ER visit, and no intravenous inotropic or vasodilator treatment for 2 weeks)
• An LVEF <= 40%, documented within 6 months prior to randomization, or > 6 months with confirmation of LVEF by local echocardiographic measurements within 2 weeks prior to randomization
• Able to give informed consent

Exclusion Criteria:

• New onset CHF (less than 3 months prior to randomization)
• Active myocarditis, hypertrophic cardiomyopathy, uncorrected primary valvular disease, restrictive cardiomyopathy, uncorrected congenital heart disease, or constrictive pericarditis
• Myocardial infarction, unstable ischemic heart disease, stroke, or coronary revascularization procedure within 4 weeks prior to randomization; or an expectation of a coronary revascularization procedure, cardiac transplant, or left ventricular assist device placement being needed within 24 weeks after randomization
• History of sudden arrhythmic syncope or sustained ventricular arrhythmia, unless the patient has an implantable cardioverter defibrillator (ICD) for at least 12 weeks prior to randomization; history of clinically significant heart block, unless the patient has had a pacemaker at least 12 weeks prior to randomization
• History of cardiac resynchronization therapy in the last 12 weeks prior to randomization or expectation of cardiac resynchronization therapy or ventricular mechanical assistance needed within 24 weeks after randomization
• History of cardiac transplant
• Heart rate < 50 beats per minute or > 130 beats per minute
• Systolic blood pressure <= 80 mm Hg
• Serum creatinine => 2.5 mg/dL
• Treatment with intravenous vasodilators (including nesiritide) or inotropes within 2 weeks prior to randomization
• Receipt of any other investigational agent or device within 4 weeks prior to randomization
• Diagnosis of other non-cardiac underlying medical conditions expected to impact their mortality within 24 weeks after randomization
• Drug or alcohol dependence, or other conditions which may affect study compliance
• History of thyroid disorders of any form within 24 weeks prior to randomization
• Use of thyroid supplements (levothyroxine, liothyronine, etc.) or any preparation containing thyromimetic agents within 24 weeks prior to randomization
• Supraventricular arrhythmia refractory to conventional treatment, as judged by the investigators