Heart failure is present when the heart is unable to eject enough blood from its chambers into the circulation to satisfy the needs of the body. Heart failure is responsible for over one million admissions to hospitals in the United States.
Heart failure is usually the result of a diseased heart. The most common cause is a very weak heart muscle. The heart muscle is the strongest muscle in the body. During an average life span, the heart beats about 2.5 billion times, pumping more than 227 million liters of blood. If this work could be accomplished in one moment, it would be sufficient to lift a weight of about 400 million pounds off the ground. If the heart muscle is severely weakened and unable to adequately expel the blood brought to the left or right ventricle, blood backs up in the veins that drain into the left or right side of the heart.
Oxygenated blood flows from the lungs through veins to the left atrium and left ventricle (see Fig. 1). These veins in the lungs can become overdistended with blood and leak fluid (sodium and water) into the lung tissue. This is called lung edema due to left heart failure. If heart failure con¬tinues for several days, the fluid may also accumulate in the space between the lungs and the chest wall. This is called pleural effusion (water on the lungs).

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