Targeting Acute Congestion With Tolvaptan in Congestive Heart Failure

This study will be a randomized, double blind, placebo controlled, multi-center clinical trial of patients with signs and symptoms consistent with AHF within 24 hours of presentation at Emergency Department. A total of approximately 250 patients will be enrolled in the trial. Patients will be randomized in a 1:1 ratio to either of 2 treatment regimens: * Fixed-dose IV furosemide (1 x total daily oral dose given intravenously in divided doses Q12 hours OR 40 mg IV Q12 hours, whichever is greater) + oral Tolvaptan (given at 0, 24 and 48 hours) * Fixed-dose IV furosemide (1 x total daily oral dose given intravenously in divided doses Q12 hours OR 40 mg IV Q12 hours, whichever is greater) + oral placebo (given at 0, 24 and 48 hours) The study treatment regimen will be administered from randomization through 48 hours, at which point Tolvaptan/placebo will be discontinued and all diuretic treatment will be adjusted at the treating physician's discretion. The primary endpoint will be the proportion of patients with at least moderate improvement in dyspnea by Likert scale at both 8 AND 24 hours AND without the need for escalation of therapy due to worsening heart failure (rescue therapy) or death within 24 hours. Patients will be followed daily for the duration of hospitalization or for 7 days (whichever is shortest). All patients will have Day 30 follow up phone contact for assessment of vital status and interval hospitalizations.