In congestive heart failure or heart failure the heart cannot pump enough blood through the body. The heart cannot fill with enough blood or pump with enough force, or both. Heart failure develops over time as the pumping action of the heart gets weaker. It can affect the right, the left, or both sides of the heart. Heart failure does not mean that the heart has stopped working or is about to stop working.

In most cases, heart failure affects the left side of the heart when it cannot pump enough oxygen-rich blood to the rest of the body. When heart failure affects the right side, the heart cannot pump enough blood to the lungs, where it picks up oxygen.

When the heart is weakened by heart failure, blood and fluid can back up into the lungs, and fluid builds up in the feet, ankles and legs. People with heart failure often experience tiredness and shortness of breath.