Because the heart is a double pump, each side can initially fail independently of the other. If the left side fails,pulmonary congestion occurs. The right side of the heart continues to propel blood to the lungs, but the left side does not adequately eject the returning blood into the systemic circulation. Thus, blood vessels in the lungs become engorged with blood, pressure within them increases, and fluid leaks from the circulation into the lung tissue, causing pulmonary edema. Shortness of breath and difficulty breathing in a prone position may occur.
If the right side of the heart fails, peripheral congestion occurs. Blood stagnates within body organs, and pooled fluidsin the tissue spaces impair the ability of body cells to obtain adequate nutrients and oxygen and to rid themselves ofwastes. Edema is most noticeable in the extremities (feet, ankles, and fingers)