The heart is split into four parts. Two collecting chambers at the top called Atria (Atrium) and two pumping chambers at the bottom called Ventricles. The Left Atrium normally pumps to the Left Ventricle and the Right Atrium to the Right Ventricle. In Double Inlet Left Ventricle both Atria (Left and Right) pump into one big Left Ventricle. The Right Venticle is usually very small and joined (via a large hole in the wall) to the Left Ventricle. This forms a heart with two top chambers and really just one bottom chamber. Other heart defects are often present too including a narrow Pulmonary (lung) valve or Coarctation of the Aorta (narrowing of the main pipe supplying blood to the body). Double Inlet Left Ventricle will always need surgery and often multiple operations.