ukmla MCQ (SBA): Chronic Heart Failure Management

A 75-year-old man with heart failure (LVEF 35%) treated with Ramipril, Bisoprolol, and Furosemide presents with worsening ankle oedema and shortness of breath on exertion. His symptoms are stable on maximal tolerated doses of ACEi and beta-blocker. His serum potassium is 4.2 mmol/L and eGFR is 55 ml/min/1.73m². According to NICE guidelines, what medication should be considered next?