The heart is like a pump to collect venous blood from the whole body into the right atrium and right ventricle through the pulmonary artery to send to the lungs, so as to discharge extra useless carbon dioxide and breathe fresh oxygen. It makes dull red pulmonary blood become freshly red arterial blood to be back to the left atrium and left ventricle. Then, then the arterial blood was transported to all the body to supply oxygen and nutrients. The arterial and venous systems of a normal heart are completely separated. If the heart occurs malformations, venous blood may not pass through the lungs but directly send into the arterial system.

The most common cyanotic congenital heart disease is the Tetralogy of Fallot, which has four kinds of defects: 1.the pulmonary artery from the right ventricle leading to the lungs is much stenosis comparing with the normal one; 2. the location of aorta moves towards right and stays across the ventricular septum, so that the aorta which originally only accepts the left ventricular blood turns into accepting blood both from the left and right ventricular; 3. ventricular septal defect; 4. right ventricular hypertrophy. Thereupon, part venous blood from right ventricular directly flows into the left ventricular. In this way, the arterial and venous blood mix to make the Deoxygenated hemoglobin contained in superficial capillaries of mucosa in the skin be more than the normal amount, then appears the cyanosis.

It must be pointed out that cyanosis is not necessarily all caused by congenital heart disease. Any disease affecting the lungs to exchange oxygen, such as respiratory obstruction, pneumonia and empyema, as well as some drugs or foods may also cause cyanosis. A small number of infants with bad temper and long breath while crying, may also have cyanosis, but after the crying stops  and breathe freely, the cyanosis disappears, which is called breath-holding attack. A variety of cyanosis can ask for a doctor to distinguish situations clearly and get the correct diagnosis and treatment.

Comprehensively understand cyanotic congenital heart disease! edited by Heart Problems, all rights reserved, Do not copy or revise without our permission.