What is the principal sign of coronary artery disease?

Angina: At early stages it may not cause symptoms. Once blockages become more significant, chest pain and/or shortness of breath occur, usually worse with activity.

There are many: Some people have chest pain, some do not. Some never have a heart attack, others drop dead. Classic symptoms include chest pain and shortness of breath. You probably want to see your doctor, since we cannot diagnose this over the internet.