Practice question

A 70-year-old man with heart failure (LVEF 35%) is taking ramipril 10mg OD, bisoprolol 10mg OD, and furosemide 40mg OD. He remains symptomatic (NYHA class II-III) despite optimal doses of these medications. His eGFR is 55 mL/min/1.73m² and potassium is 4.8 mmol/L. According to NICE NG106, what medication should be considered next?