It should be noted that these resources represent a wide spectrum of studies and conclusions. I promote the whole food plant-based diet as recommended by Dr. Caldwell Esselstyn. These recommendations are strict but effective. The reason there are various conclusions is because of the dietary variations studied. Many "heart-healthy" diets include foods that damage endothelium. These foods are purposefully omitted here.
Nevertheless, as can be seen from the resources, there is a common thread regarding the significance of eating plant-based for heart health. It's simply that by adjusting the diet to the best and most nutritious foods and eliminating damaging foods will produce the most favorable results. I call this "heart-healing."