Heart failure happens when your heart has trouble pumping the right amount of blood through the body. This means the body will not receive the oxygen it needs to work well. When the heart is not working well, blood can back up into the lungs, neck, belly, and arms. It can also cause swelling in the legs or other parts of the body. Heart failure is a long-term problem and will get worse over time. Your doctor will work hard to treat your heart failure and to keep you as healthy as possible.