Hi welcome to the heart disorder board. First I would choose to try not to panic. Second realize that sometimes tests have false positives and false negatives. Of course a second 5 star health professional could be consulted at a 5 star hospital for any further work or testing.
Of course healthy lifestyle things such as avoiding meats, sweets, lots of fat especially the hydrogenated type and a healthy walk everyday is something I would choose.
All decisions are of course up to the individual because that is the body they have to live with and they are only given one in this life so it is important to take care of it right. One can educate themselves about the body and its proper care etc.
You need to talk to the surgeon on what all this means, or your cardiologist. You need to ask quesions when these things come up so you can gain medical knowledge. Knowledge is the key to greater health decisions and choices. And what type of surgery are you looking forward to having done. Is it bypass, or some other proceedure? Hugs for today.