A 68-year-old man presents to his GP with worsening dyspnoea on exertion. His medical history includes hypertension, and he is currently taking ramipril. On examination, bibasal crackles are heard in his chest, and he has bilateral pitting oedema up to the level of his shins. His blood pressure measures 145/89 mmHg. An outpatient echocardiogram reveals no valvular abnormalities but shows a dilated left ventricle with an estimated ejection fraction of 38%. What is the most appropriate medication to prescribe next to reduce overall mortality?
