2.1. Patients

Sixty-one consecutive patients (37 male and 24 female patients) were enrolled in this retrospective study. These patients were admitted to the Iwate Prefectural Kuji Hospital or the Critical Care and Emergency Center of Iwate Medical University Hospital between July 2011 and April 2015 with acute HF and were initially treated with loop diuretics. Patients were excluded from the study if they had received combination therapy with carperitide and tolvaptan or if they had been treated with tolvaptan or cardiotonic drugs in an outpatient setting. They were also excluded if their LV ejection fraction was ≥40% or they showed signs of renal failure (serum creatinine > 2.0 mg/dL) on admission. In addition, there were no patients who underwent intubation and mechanical respiratory support.