Hi Sue,
As mammo said, it's great that this was caught early on, and I think the worst part of it is the unknown. I had an EKG done, wore a Holter monitor, and then had an echocardiogram done several years ago. There was nothing conclusive on the echo, but the technician did notice that my heart rate changed from 90 to 100 to 110. I was also put on a beta blocker and it's solved my problems. She pretty much knew that day there was nothing for me to worry about, so while you will have to wait for official results, the techs are pretty good about finding anything serious. Additionally, I dated a guy whose coronary artery was 85% blocked and he never had to have surgery. I would say it is perfectly normal for the doctor to put you on a beta blocker, especially for the timebeing, as it's unknown for sure how blocked the artery is. It's common for anyone with a blocked artery to be put on a beta blocker, as it decreases the blood pressure and the strain on the heart. Try to relax, I'm sure all is well, and I know it's easier said than done, as I also know first-hand how scary it is!
Anxiety is not good for the heart, so I agree with the above post to follow your doctor and get the echo and go from there. Worry and stress is hard on our hearts, so try to be thankful this was caught in time and you will be fine.
Your doctor thinks you require these drugs. Go and get your echocardiogragm and worry about the rest later.