By the time a patient is seeing a cardiac surgeon, it's extraordinarily unlikely that it would be remotely responsible to advise a patient to try to treat their condition by using diet and exercise without medication.
I think that's mainly because of tradition and the difficulty involved in getting people to make a wholesale change in their diet, not because of the superiority of the medication in reversing the condition.
Your link shows a study comparing diet to placebo. In contrast, your comment talks about diet vs medication. A nuanced but important difference. To the best of my knowledge, diet-vs-medication has not been tested systematically in a high quality trial.
Another study that you might like, and which is potentially more relevant by the point you're talking with a cardiac surgeon, is the Lyon Heart Study, which actually looks at secondary prevention:
