Why can angina be felt in the anterior chest wall and the left arm?

The brain cannot sometimes identify the direct location of where pain is coming from. In angina (ischaemic pain of the heart), the pain is transmitted via nerve fibres to vertebrae levels T1-4, when these nerves converge there can be some confusion of the origin of the pain and thus the dermatomes of T1-4 can be affected (left arm, jaw, chest wall ect)