A 78-year-old man with a history of heart failure (ejection fraction 35%) presents with increasing shortness of breath and ankle swelling over the past week. His current medications include bisoprolol, ramipril, and furosemide 40mg daily. Examination reveals bilateral pitting oedema to the mid-shin and crackles at both lung bases. His weight has increased by 3 kg. What is the most appropriate next step in management?