Natriuretic Peptide System as Therapy in Human Preclinical Left Ventricle Dysfunction

Inclusion criteria for normal control group: * ejection fraction of greater 50% * normal Doppler diastolic function with no clinical signs or symptoms * history of cardiovascular and renal disease * no prior use of any cardiovascular medications. Inclusion criteria for pre-systolic dysfunction group: * ejection fraction of less than 40% with no clinical signs or symptoms of congestive heart failure * ability to perform a 6-minute walk of \> 450 meters * if subjects are not able to walk 450 meters due to pain in hips and knees and not fatigue or shortness of breath, then they will still qualify for the study * subjects will all be on stable doses of ACE inhibitor for two weeks prior to the active study date * previously prescribed cardiovascular medications are allowed, however, all medications must be at stable doses two weeks prior to the study date. Inclusion criteria for pre-diastolic dysfunction group: * ejection fraction of greater than 50% with moderate or severe diastolic dysfunction as assessed by Doppler echocardiography * no signs or symptoms of congestive heart failure * ability to perform a 6-minute walk of \> 450 meters * if subjects are not able to walk 450 meters due to pain in hips and knees and not fatigue or shortness of breath, then they will still qualify for the study * previously prescribed cardiovascular medications are allowed, however, all medications must be at stable doses two weeks prior to the study date. Exclusion criteria for all groups: * myocardial infarction within 3 months of screening * unstable angina within 14 days 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 * total bilirubin of \> 1.5 mg/dL or other liver enzymes \>1.5 times the upper limit of normal * serum creatinine of \> 3.0 mg/dL * serum sodium of \< 125 mEq/dL or \> 160 mEq/dL * serum potassium of \< 3.5 mEq/dL or \> 5.0 mEq/dL * serum digoxin level of \> 2.0 ng/ml * systolic pressure of \< 85 mmHg * hemoglobin \< 10 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 * in the opinion of the investigator, is unlikely to comply with the study protocol or is unsuitable for any reason.