ACE and heart failure: HF: Heart failure; IQR: Interquartile range; NYHA: New York Heart Association; ACEi: Angiotensin-converting enzyme inhibitor; ARB: Angiotensin II receptor blocker; BNP: Brain natriuretic peptide; NT-proBNP: N-terminal-pro brain natriuretic peptide; 6MWT: Six-Minute Walk Test; KCCQ-12= Kansas City Cardiomyopathy Questionnaire-12