CR Aim #2 - AT1 Receptor Blockade & ACE Inhibition Effect on Humoral Function

Inclusion Criteria: * Left ventricular ejection fraction of equal or less than 40% assessed by echocardiography, nuclear scan, MRI or left ventriculogram within the past 48 months. * Stable New York Heart Association (NYHA) class II and III symptoms as defined by: no change in NYHA symptoms over the past 3 months, on stable doses of ACE inhibitor, beta blocker, digoxin and furosemide over the last 4 weeks and no episode of decompensated CHF over the past 6 months. * Calculated creatinine clearance of equal or less than 80 ml/min and greater than 20 ml/min, using the MDRD formula assessed within the past 48 months and a confirmatory calculated creatinine clearance equal or less than 80 ml/min and greater than 20 ml/min at the time of enrollment. Subjects who are already taking AT1 receptor blocker will be excluded. Aldosterone antagonist, antiarrhythmic medications and other vasodilators will be allowed; however, all medications must be at stable doses 4 weeks prior to enrollment. Subjects taking nonsteroidal anti-inflammatory drugs (NSAIDs) except aspirin will not be able to increase their medication dose for the duration of the study. Subjects will be excluded if they have had a prior diagnosis of intrinsic renal disease, including renal artery stenosis of \> 50%, or if they meet any one of the exclusion criteria listed below. Exclusion Criteria: * Prior diagnosis of intrinsic renal diseases including renal artery stenosis of \> 50% * Peritoneal or hemodialysis within 90 days or anticipation that dialysis or ultrafiltration of any form will be required during the study period * Hospitalization for decompensated CHF during the past 6 months * Subjects that are taking AT1 receptor blockers * Myocardial infarction within 6 months of screening * Unstable angina within 6 months of screening, or any evidence of myocardial ischemia * Significant valvular stenosis, hypertrophic, restrictive or obstructive cardiomyopathy, constrictive pericarditis, primary pulmonary hypertension, or biopsy proven active myocarditis * Severe congenital heart diseases * Sustained ventricular tachycardia or ventricular fibrillation within 14 days of screening * Second or third degree heart block without a permanent cardiac pacemaker * Stroke within 3 months of screening, or other evidence of significantly compromised CNS perfusion * ALT \>1.5 times the upper limit of normal * Serum sodium of \< 125 mEq/dL or \> 160 mEq/dL * Serum potassium of \< 3.5 mEq/dL or \> 5.7 mEq/dL * Serum digoxin level of \> 2.0 ng/ml * Hemoglobin \< 9 gm/dl * Other acute or chronic medical conditions or laboratory abnormality which may increase the risks associated with study participation or may interfere with interpretation of the data * Received an investigational drug within 1 month prior to dosing * Patients with an allergy to iodine. * Female subject who is pregnant or breastfeeding * In the opinion of the investigator, is unlikely to comply with the study protocol or is unsuitable for any reasons