The Use of Tolvaptan to Prevent Renal Dysfunction in High Risk Patients With Heart Failure-Pilot Study

Inclusion Criteria: * ≥ 18 years old * Prior clinical diagnosis of systolic heart failure (EF \< 40% within the past 18 months) with daily home use of oral loop diuretic for at least one month. * Daily oral dose of furosemide ≥ 40 mg and ≤ 240 mg (or equivalent) * Identified within 24 hours of hospital admission * Heart failure defined by at least 1 symptom (dyspnea, orthopnea, or edema) AND 1 sign (rales on auscultation, peripheral edema, ascites, pulmonary vascular congestion on chest radiography) * Anticipated need for IV loop diuretics for at least 48 hours * Likely requires daily net urine output in the range of 1-3 L/day for over a 72-96 hour time period. * Albumin level \< 3.5 g/dL * Willingness to provide informed consent Exclusion Criteria: * Received or planned IV vasoactive treatment (inotropes, vasodilators) or ultra-filtration therapy for heart failure * BNP \< 250 ng/ml or NT-proBNP \< 1000 mg/ml (if drawn for clinical purposes) * Systolic BP \< 90 mmHg * Serum creatinine \> 3.0 mg/dl at baseline or renal replacement therapy or creatinine clearances \< 10 mL/min * Serum sodium \> 145 mEq/L * Acute coronary syndrome within 4 weeks * Anticipated need for coronary angiography or other procedures requiring IV contrast. * Patients receiving any of the following drugs: clarithromycin, ketoconazole, itraconazole,ritonavir, indinavir, nelfinavir, saquinavir, nefazodone, telithromycin, erythromycin, fluconazole, aprepitant, diltiazem, verapamil, cyclosporine, and grapefruit juice. * Pregnant or nursing patients.