Aims We aimed to determine the relation between baseline systolic blood pressure (SBP), change in SBP, and worsening renal function (WRF) in acute heart failure (AHF) patients enrolled in the Pre-RELAX-AHF trial. Methods and resultsThe Pre-RELAX-AHF study enrolled 234 patients within 16 h of admission (median 7 h) for AHF and randomized them to relaxin given intravenous (i.v.) for 48 h or placebo. Blood pressure was measured at baseline, at 3, 6, 9, 12, 24, 36, and 48 h and at 3, 4, and 5 days after enrolment. Worsening renal function was defined as a serum creatinine increase of