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."
https://nutritionfacts.org/video/plant-based-treatment-for-angina/
https://www.virtua.org/articles/prevent-and-reverse-heart-disease-with-a-plant-based-diet
https://www.mamasezz.com/blogs/news/prevent-and-reverse-heart-disease-with-a-plant-based-diet
https://vitalrecord.tamhsc.edu/reversing-effects-of-chronic-disease-through-a-whole-food-plant-based-diet/
https://www.hopkinsmedicine.org/news/media/releases/study_suggests_medical_errors_now_third_leading_cause_of_death_in_the_us
https://www.sciencedaily.com/releases/2019/01/190131084238.htm
https://www.independent.co.uk/life-style/who-were-the-world-s-very-earliest-vegans-a7668831.html
https://nutritionfacts.org/2016/11/15/the-natural-human-diet/