Blood for the measurement of renin, angiotensin II (Ang II), aldosterone (Aldo), endothelin (ET)-1, norepinephrine, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), cGMP, C reactive protein, tumor necrosis factor (TNF)-alpha, matrix metalloproteinase (MMP)-2 and tissue inhibitor of metalloproteinase (TIMP)-2 will be drawn before the initiation of IV nesiritide, six hours into the infusion before the initiation of ACEI and just before completion of the 72 hour infusion. The window for the blood draw for the six hour time point would be +/- 1 hour and the 72 hour time point would be +/-1 hour or just prior to discharge but not less than 66 hours.