Background: Oral mineralocorticoid receptor antagonists have failed to prove their efficacy for decongestion and potassium homeostasis in acute heart failure. Intravenous mineralocorticoid receptor antagonists have yet to be studied.Aim: The aim of this study was to confirm the safety of high-dose potassium canrenoate in association with classic diuretics in acute heart failure.Methods: This retrospective single-centre study included consecutive patients who were hospitalized with acute heart failure between 2013 and 2018. One hundred patients with overload treated with the standardized diuretic protocol from the CARRESS-HF trial were included. There were no exclusion criteria relating to creatinine or kalaemia at the time of admission. Two groups were constituted on the basis of potassium canrenoate posology: a low-dose group (<300mg/day) and a high-dose group (≥300mg/day); the groups were similar in terms of baseline characteristics.Results: Mean daily potassium canrenoate doses were 198mg/day (range 100-280mg/day) in the low-dose group and 360mg/day (range 300-600mg/day) in the high-dose group. There was no significant difference between the high-dose and low-dose groups in terms of mortality, dialysis, renal function, hyperkalaemia, haemorrhage, sepsis or confusion.Conclusions: Potassium canrenoate at high doses can be used safely in association with standard diuretics in acute heart failure, even in patients with altered renal function. A prospective study is required to evaluate the efficacy of high-dose potassium canrenoate in preventing hypokalaemia and improving decongestion.