What Causes A Fast Pulsating Sensation On The Chest Area?

Hi, lately I been have this fast beating under my left breast to my chest. I was recently diagnosed with Amenia and doctor told me my blood pressure was slightly high. I been taking propranolol hcl 20MG tabs and Ferrex 150 polysaccharide-iron complex capsules. Couple weeks before I went to the ER and they did a chest x-ray and Ekg and it came back find.