Prevention of coronary artery disease is less than perfect. For you, the prevention is secondary inasmuch as we know you have atherosclerotic coronary artery disease. The prevention approaches include cholesterol and LDL in the ideal range, normal blood pressure, no smoking, no exposure to secondary smoke, avoiding excessive and preventable stress, regular physical activity, a Mediterranean type diet, a diet heavy on fruits and vegetables, weight in the ideal range. There are certain medications that are considered to protect the heart. Some doctors advise modest amounts of red wine. It is also desirable to have a good heredity and not to have diabetes.
Screening tests are of questionable value, and it is more important to see a good cardiologist at reasonable intervals.
Please keep in mind that I am unable to diagnose medical conditions online.