In people with heart failure, the heart does not pump blood efficiently.

When your heart isn't pumping efficiently, it can't get enough blood out to your body, and that can make you tired.

If one of the heart chambers contracts out of synchrony, it can interfere with your heart's ability to pump blood efficiently.

Instead, the left heart fails to pump blood efficiently, leading to pooling of blood in the lungs.

And, like an aging heart, a long-established group may need an occasional infusion of new blood to keep it pumping efficiently.

Heart failure occurs when your heart loses its ability to pump blood efficiently.

The heart's contractions become uncoordinated, preventing the organ from pumping blood efficiently.

Most gases are heavy enough to be well pumped but it is difficult to pump hydrogen and helium efficiently.

The heart muscle is weakened and cannot pump blood efficiently, leading to heart failure.

But the oversized, misshapen heart cannot pump blood efficiently, and the struggle may turn into a vicious cycle of deterioration.