Look up Dr Caldwell Esselstyn. He’s a doctor at the Cleveland Clinic who has consistently used diet to reverse his patients’ heart disease. It’s a low fat, low salt plant based diet. Dr McDougall is another. They both have a number of papers on the subject.

Edit: I’m not sure if McDougall’s papers are specifically on heart disease, actually, and can’t look it up conveniently at the moment. But he’s covered the topic in great depth.