When you have heart failure, your body will adapt to try and keep up with the amount of blood your body needs. This is known as compensation
Your heart will:
Your body will also try to increase the amount of circulating blood and re-direct blood flow away from your muscles to your brain and other vital organs.
While your body can compensate for a long time, its efforts are actually doing more harm than good. Since your heart is already weak, these changes make your heart work even harder and end up weakening it even more.