Welcome to HCM,
You are almost 12 years after by pass surgery,which is very good revascularization procedure but basic disease of atherosclerosis
continues and after so many years there are 3 arteries blocked.
If it is not possible to do angioplasty
, there are very good drugs for angina
and blood thinner medicines you will be angina free and also nature forms new vessels known as collateral and blood supply to heart is maintained.
You will be able to live normally ,please do not lose hope and continue to live in healthy life style,and have faith in almighty.