Heart failure is a severe medical condition characterized by the heart’s inability to pump blood effectively. Examples of the different types of heart failure are right-sided, left-sided, and congestive heart failure. In congestive and right-sided heart failure, individuals may experience a significant reduction in the flow of blood out of the human heart. 
When there is a reduction in the blood flow out of the heart, it may cause the blood to flow back into the veins. Ultimately, this leads to a buildup of fluid in tissues in the ankles. Aside from ankles, heart failure affects the kidneys due to reduced ability to remove salt and water from the body, contributing to edema.