⁃ Patients who meet the below inclusion criteria will be randomized within 12 h after presentation to the hospital

• Age of ≥20 and \<90 years

• Hospitalized with a diagnosis of acute heart failure, requiring intravenous loop diuretic therapy, and with all of the following characteristics:

• i. Dyspnoea at rest or induced by slight exertion ii. At least two of the following findings: jugular venous distention, pulmonary rales, lower leg edema, and pulmonary congestion on chest X-ray iii. If the patient has a sinus rhythm at the time of admission, BNP ≥350 pg/mL or NT-proBNP ≥1400 pg/mL; if the patient has atrial fibrillation at the time of admission, BNP ≥500 pg/mL or NT-proBNP ≥2000 pg/mL. For patients taking an angiotensin receptor neprilysin inhibitor, only the reference value for NT-proBNP will be applicable.

• At least one of the following characteristics:

• i. eGFR \<60 mL/min/1.73m2, as calculated using the CKD Epidemiology Collaboration for JapaneseModification of Diet in Renal Disease formula ii. Already taking ≥40 mg of oral furosemide during the period before hospitalization. For patients on loop diuretics other than furosemide, the following conversion should be used: oral furosemide 20 mg = oral azosemide 30 mg = oral torasemide 5 mg.

• iii. Urine output of \<300 mL during the 2 h following an appropriate dose of intravenous furosemide administered after hospitalization. An appropriate dose of intravenous furosemide is 20 mg for patients who have not been taking furosemide regularly before hospitalization and is the same as, or greater than, the daily oral dose for patients who have been taking furosemide regularly before hospitalization.

• Provided written consent to participate in the study