Omega-3 fatty acids are also abundant in fish, and according to the American Heart Association, they can lower the risk of developing abnormal heart rhythms and can also decrease the levels of triglycerides in the blood.
A recent study found that walnuts also have about twice the amount of antioxidants as other nuts. Eating foods rich in antioxidants can help reduce the risk of heart disease, according to the Cleveland Clinic.
"Avocados are a super-fruit that has lots of monounsaturated fat," said Stowell.
Avocados also have a lot of vitamins, fiber and potassium. According to the U.S. Centers for Disease Control and Prevention, avocados have 60 percent more potassium than bananas.
One of the healthiest nutrients in avocados and other heart-friendly foods is fiber.
"Fiber helps cleanse the digestive tract of potentially dangerous fats," said Ragno. "Snacks that are high in fiber include oats, grains, beans, fruits and vegetables."
Fiber also helps lower cholesterol, which can help lower the risk of cardiovascular disease.
Dietary guidelines say women should consume 25 grams of fiber per day and men should consume 38 grams, according to the Academy of Nutrition and Dietetics, formerly the American Dietetic Association.