This forces the heart to pump an extra amount of blood to the lungs. This extra effort in turn causes the heart to enlarge. In addition, the body receives less oxygen since it receives red blood that is mixed with low-oxygen blood. Because of the high volume of blood that is pumped to the lungs, high blood pressure may occur there, resulting in damage to the lungs and blood vessels. Surgical repair of an AV canal usually restores blood circulation to normal.
Heart defects are serious problems.
In their most severe form. Even defects that do not need immediate surgery can drastically shorten life if left un-treated. Over time, the blood vessels will become scarred, and, if not treated soon enough, will eventually income so narrow that not enough blood can reach the lungs. This condition is fatal. Heart failure does not mean the heart is stopping, but rather that it cannot keep up with the body's needs.