Grant's condition

The name of the congenital heart defect that Grant was diagnosed with is Total Anomalous Pulmonary Venous Connection,with obstruction. In TAPV, the pulmonary veins that bring oxygen-rich blood from the lungs back to the heart aren't connected to the left atrium. Instead, the pulmonary veins drain through abnormal connections to the right atrium.

In the right atrium, oxygen-rich blood from the pulmonary veins mixes with venous blood from the body. Part of this mixture passes through the atrial septum into the left atrium. From there it goes into the left ventricle, to the aorta and out to the body. The rest of the poorly oxygenated mixture flows through the right ventricle, into the pulmonary artery and on to the lungs. The blood passing through the aorta to the body doesn't have enough oxygen, which caused Grant to look blue.

In surgery, the pulmonary veins were reconnected to the left atrium and the atrial septal defect was closed. What makes Grant's condition more serious than most cases of TAPV is that he also developed an obstruction. The obstruction had and continues to have an effect on the lungs.