Hello and Welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here is my advice.
The pain that you feel on your left arm, may be related to heart isssues but it can also be related to the rotator cuff(the group of muscles and tendons that surround the shoulder joint)injury.
Commonly when the left arm pain is caused by the heart it is accompained by
chest pain, sweating or
difficulty breathing and sometimes it gets worse during activity.
When the pain is related to the rotator cuff usually gets worse with the movement of the arm.
First of all it's very important for you to
consult a cardiologist make an ECG, and then if the doctor decides, you can also perform a
stress test that shows how your heart works during actvity. You have to measure the blood pressure, perform blood tests( blood glucose,
cholesterol, tryglicerides).
After that if after these examinations it turnes out that the pain is probably neuromuscular you can consult an orthopedist.
Hope I have answered your query.
Let me know if I can assist you further.