Mrs. Roberts is a 54-year-old woman whom you have seen in the clinic on and off for a few years. She now presents with complaints of migraines and lethargy, symptoms that have worsened over the last several months. She usually takes paracetamol for her headaches, but of late, this approach has not provided much relief. She also reports occasional ‘twinges’ in the chest that last a few seconds, and sometimes for a minute or two.