Fish Oil

The unsaturated fats in fish are called omega-3 fatty acids. Omega-3 fatty acids and other nutrients in fish may benefit heart health and reduce the risk of dying of heart disease.
https://www.mayoclinic.org/diseases-conditions/heart-disease/in-depth/omega-3/art-20045614

Fish oil supplements have been promoted as easy way to protect the heart, ease inflammation, improve mental health, and lengthen life.
https://www.health.harvard.edu/blog/fish-oil-friend-or-foe-201307126467

Fish oil has long been a popular supplement to protect against heart disease. It contains high levels of omega-3 fatty acids, primarily EPA and DHA, which reduce inflammation and lower triglyceride levels.
https://www.webmd.com/heart-disease/news/20180925/can-fish-oil-cut-danger-of-high-risk-heart-issues#1

According to the AHA, these heart patients should add a fish oil supplement to their diet to help prevent future heart-related events. Fish oil contains omega-3 fatty acids, which, when consumed by eating fatty fish, can cause blood vessel relaxation, reduced blood clotting, reduced inflammation and possibly stabilization of heart rhythm.
https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/fish-and-omega-3-fatty-acids

Eicosapentaenoic Acid (EPA)

Eicosapentaenoic acid (EPA) is one of several omega-3 fatty acids. It is found in cold-water fatty fish, such as salmon. It is also found in fish oil supplements, along with docosahexaenoic acid (DHA). Omega-3 fatty acids are part of a healthy diet that helps lower risk of heart disease.
https://www.mountsinai.org/health-library/supplement/eicosapentaenoic-acid-epa

Eicosapentaenoic acid is used in combination with docosahexaenoic acid (DHA) in fish oil preparations for a variety of conditions, including preventing and reversing heart disease, and decreasing irregular heartbeats; as well as asthma, cancer, menstrual problems, hot flashes, hay fever, lung diseases, lupus, and kidney disease caused by an immune reaction.
https://www.emedicinehealth.com/eicosapentaenoic_acid/vitamins-supplements.htm

As a supplement, EPA is most commonly used for heart disease, preventing adverse events after a heart attack, depression, and menopause.
https://www.webmd.com/vitamins/ai/ingredientmono-994/epa-eicosapentaenoic-acid

Experts have found that people who eat foods with high levels of 2 of the omega-3 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), have low rates of CHD.
https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=1&contentid=3054

Docosahexaenoic Acid (DHA)

DHA is the active component in fish. Not only does fish oil reduce triglycerides in the blood and decrease thrombosis, but it also prevents cardiac arrhythmias.
https://www.ncbi.nlm.nih.gov/pubmed/10479465

DHA plays a key role in the development of eye and nerve tissues. DHA may also reduce the risk of heart and circulatory disease by decreasing the thickness of the blood and lowering blood levels of triglycerides.
https://www.webmd.com/vitamins/ai/ingredientmono-864/dha-docosahexaenoic-acid

Docosahexaenoic acid lowers cardiac mitochondrial enzyme activity by replacing linoleic acid in the phospholipidome.
http://www.jbc.org/content/293/2/466.full

DHA is also taken by mouth for diabetes, coronary artery disease (CAD), stroke, high levels of cholesterol and fats in the blood, high blood pressure, and cancer including breast and prostate cancer. It is also used for a type of fatty liver not related to drinking alcohol, obesity, ear infections, and learning problems in children.
https://www.rxlist.com/docosahexaenoic_acid/supplements.htm