True angina can be very serious, but if it is just the pain, not an actual heart problem it may be caused by muscle tension known as Trigger Points which you can locate on your back in the iliocostalis muscles which run along each side of your spine. They can also cause pain mimicking pleurisy, appendicitis, kidney stones, tumors, rib inflamation, ligament tear or disc problems. If you put a tennis ball inside of a long sock (to hang onto it), you can massage the muscles on your back by pressing into a wall. Trigger points need direct pressure for minimum 15 seconds or longer.