Yes this is a question for your doctor.Here no one can say accurately about your heart condition because it needs some medical test.So accurate condition of your heart is only shown by medical test.
That is a question for your Cardiologist, it would be irresponsible for anyone here to say you can return to work, not knowing the full history and circumstances surrounding your heart. It is certainly a great thing that your heart has improved so dramatically over the last few months. What you wouldn't want to do is over work your heart, so you get into heart failure, and this is why it is a question for your Cardiologist.
I'm sorry it isn't the answer you want, but you need expert advice on this.