An 81-year-old man with chronic stable angina was taking asprin 75mg OD, simvastatin 40mg OD, bisoprolol 2.5mg OD, nicorandil 10mg BD, and lisinopril 2.5mg OD. He was a non-smoker and was not diabetic. He had been unwell for 4 weeks with generalized lethargy, increasing exertional shortness of breath and postural light-headedness. During this time he had 3 days of loose dark stools and mild upper abdominal discomfort, which had now settled. Subsequently, he reported his angina was occurring on minimal exertion. On examination, he was pale, with a sinus tachycardia of 105beats/ min. His BP was 130/70 sitting and 105/60 standing. Respiratory and abdominal examinations were unremarkable, but he declined a digital rectal examination. While in the clinic, he had an episode of suspected angina and an ECG confirmed dynamic anterior lead t-wave inversion. This settled with use of the GTN spray. Which of the following is the most appropriate immediate course of action?