au-amc MCQ (SBA): Heart failure with reduced ejection fraction

A 64-year-old man with ischaemic cardiomyopathy (left ventricular ejection fraction 32%) presents for review. He has NYHA class II symptoms but is euvolaemic on examination. Current medications are perindopril, frusemide, low-dose spironolactone and atorvastatin. His blood pressure is 118/70 mmHg and heart rate 76 bpm, sinus rhythm. According to Australian heart failure management recommendations, which additional medication is most likely to improve his long-term survival?