The heart has two sides: a left side and a right side. Within these sides lie the chambers of the heart – there are two pumping chambers (the ventricles) and two collecting chambers.
In a normally-developed heart, the oxygen-poor (blue) blood returns to the right atrium from the body, enters the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. The oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle and is then pumped out to the body through the aorta.
For children with single ventricle anomalies, one of the ventricles has not developed properly or the inside arrangement of the two ventricles is too complicated to be separated into two.
The red blood will then mix with the blue blood, causing cyanosis or blueness, because the body receives less oxygenated blood. In order to thrive, babies born with single ventricle anomalies will need surgical intervention.