How long people with chest pain should wait before calling an ambulance is a question familiar to general practitioners and emergency doctors. The answer is complicated by the use of sublingual nitrate sprays, which promptly relieve the pain of stable angina.1 Ideally, patients would be able to distinguish stable angina from a potentially life threatening acute coronary syndrome, but in reality they do not. Therefore the decision about when to call an ambulance needs to balance between an overly cautious strategy that could overburden emergency medical services and one where delayed action leads to higher morbidity and mortality. The balance is difficult to find because international guidance indicates that consensus has not been reached, even among cardiologists.2 3 4

The British Heart Foundation advises patients with known ischaemic heart disease that chest pain that lasts more than 15 minutes is probably a heart attack.2 Within this time patients are advised to use their glyceryl trinitrate (GTN) spray three times at five minute intervals before calling an ambulance. Yet a recent British Heart Foundation campaign advises members of …