I am probably silly to lose sleep over this, but I don't want to have the same problems as my ancestors. How can I prevent heart attack?

Diet, exercise, no smo. Since you cannot change your parents, the best way to avoid coronary disease is to eat right: fish, fruits and veggies, whole grains; exercise regularly and don't smoke. Taking low dose Aspirin daily has some merit, but can cause bleeding.
Good habits. There s no substitute for proper nutrition and regular exercise. Eat as many natural foods as possible including meats vegetables and fruits and avoid processed foods.
The Texas Two Step. Ok, inflation and all: 5 step. Cholesterol check. Blood pressure monitored. No smoking poison fire sticks. Exercise like your life depends on it. Decrease salt and fats.