Heart disease is the leading cause of death for both women and men in the U.S.A. Fortunately, the evidence is compelling that a plant-based diet can reduce the risk significantly. In both women and men, higher consumption of fruits and vegetables is associated with a decreased incidence of heart disease. One study concluded by recommending the consumption of > 5 servings/day of fruits and vegetables. Soy is also protective. The FDA authorizes the use, on food labels and in food labeling, of health claims on the association between soy protein and reduced risk of CHD. Fiber, found only in plants reduces coronary heart disease mortality.  
 
On the other hand, as you are probably already aware, consumption of red and processed meat increases the risk of heart disease as well as a number of other disorders. Similarly, decreasing dairy consumption reduces risk of cardiovascular disease. 
 
We are fortunate that there are measurable risk factors for heart disease such as blood pressure and cholesterol level. Here are a couple of studies on how vegan/vegetarian diets improve blood pressure (1,2). Plant-based diets and dietary fiber lower cholesterol levels. Learn more about cardiovascular disease markers in vegans here.