That is a pretty high heart rate after just four minutes, but there are many possible causes, and only your doctors know your medical history and have examined and tested you. No one here is capable of even providing a good guess for you.
Your doctor should have scheduled a follow up visit to discuss your results (if that hasn't happened yet, call his office and ask about it). At that point, you will learn what is going on.
Bring a notepad and a pen to this appointment, so you be able to jot down both questions and answers.