A 74-year-old man with known heart failure with reduced ejection fraction (HFrEF) is reviewed in clinic. His current medications are Bisoprolol, Ramipril and Furosemide. He remains symptomatic with NYHA class II–III breathlessness. His renal function is stable and serum potassium is 4.6 mmol/L. According to current guidance, which additional disease-modifying treatment should be considered next?