When your heart doesn't pump normally, adequate blood (oxygen and nutrients) may not reach your body tissues. When this occurs, the body believes that there is not enough fluid inside its vessels. The body's hormone and nervous systems try to make up for this (compensate) by increasing blood pressure, holding on to salt (sodium) and water in the body, and increasing heart rate. These responses are the body's attempt to compensate for the poor blood circulation and backup of blood.

• The nervous system. The sympathetic nervous system releases substances called catecholamines into the bloodstream. These substances cause the blood vessels to constrict and speed up the heart rate.
• Hormone systems. When the body thinks it needs more fluid in its blood vessels, it releases specific chemicals (renin, angiotensin, and aldosterone) that cause the blood vessels to constrict. In addition, these hormones cause the body to retain more sodium and water.
• Change in heart size (remodeling). The heart gets larger with heart failure. While this helps the heart pump more blood early in the disease, in the later stages of the disease a larger heart muscle may not pump blood as well.

These responses may help your body adjust to the effects of heart failure in the short term; however, over time they actually make heart failure worse by further enlarging the heart and reducing the pumping ability of the heart.

See more on how your body compensates for heart failure.