Congestive heart failure is not common in children but can occur due to certain congenital heart defects, some acquired heart diseases such as rheumatic fever or Kawasaki disease, or a cardiomyopathy.
Poor pumping of the left ventricle raises the blood pressure in the ventricle during the short rest period between heart contractions. This causes increased blood pressure in the lungs. Small amounts of blood plasma are forced out of the lungs’ blood vessels into the lung tissue (the lungs become “wet” or “congested” with blood, similar to a dry sponge becoming wet).
Over time, the increased pressure in the lungs affects the pumping ability of the right ventricle. Eventually, the diseased or damaged left ventricle is unable to pump enough blood to the rest of the body. Other organs in the body, particularly the kidneys, sense this decrease in blood flow and attempt to make up for it by increasing the volume of blood. The combination of poor pumping by the heart and the extra fluid in the blood vessels leads to more leakage of plasma fluid through the vessel walls into the body tissues.