A 72-year-old man with long-standing hypertension presents with progressive exertional dyspnoea and ankle swelling. Echocardiography shows LVEF 30% and global hypokinesis. He is euvolaemic, blood pressure is 110/70 mm Hg and heart rate 72/min. He is not on any heart failure medications. According to CCS heart failure guidelines, which class of medication should be started first-line (assuming no contraindications)?