Mechanisms of Improvement With Beta-Blocker Treatment in Heart Failure

Inclusion Criteria: 1. Patients 18 years of age or older. 2. Man or nonpregnant women (only women who are postmenopausal, surgically sterile or practicing an acceptable method of contraception) 3. Patients with dilated nonischemic cardiomyopathy with LVEF\< 35% and NYHA Class III-IVa heart failure 4. Patients on standard stable medical therapy with Ace inhibitors (or hydralazine and nitrates or Angiotensin II Receptor blockers if Ace-intolerant), diuretics and or digoxin for at least 1 month prior to enrollment in the study. 5. Heart failure symptoms have to be present for at least 3 months 6. Written informed consent Exclusion Criteria: 1. Ischemic heart disease documented by cardiac catheterization with any coronary obstructive lesion \> 50% stenosis, history of myocardial infarction, coronary artery bypass surgery , percutaneous coronary angioplasty or stenting 2. Uncorrected primary valvular disease, obstructive or restrictive cardiomyopathy. 3. Systolic blood pressure \>170 or \<85 mm Hg or diastolic blood pressure \>100 mm Hg; heart rate \<50 bpm. 4. Sick sinus syndrome or advanced heart block (unless treated by a pacemaker), symptomatic or sustained ventricular tachycardia not controlled by antiarrhythmic drugs or an implantable defibrillator 5. Cor pulmonale, obstructive pulmonary disease requiring oral bronchodilator or steroid therapy 6. Active malignancy, or a systemic or terminal disease that would limit physical function or survival during the trial 7. Active and known drug or alcohol dependence or any factors that will interfere with the study conduct or interpretation of results. 8. Clinically important hepatic or renal disease; or any condition other than heart failure that could limit survival 9. Platelet count \<100 000 mm3 or white blood cell count \<3000 mm3, INR (international normalized ratio) \>1.7 10. Current treatment with beta-blocker, beta-agonist, verapamil, chronic cyclic or continuous inotropic therapy, or use of an investigational drug within 30 days of entry into the challenge phase 11. History of drug sensitivity or adverse reactions to beta-blockers 12. Unwillingness to cooperate or give written informed consent, pregnant or lactating women