Complete endocardial cushion defects are typed as partial types, including transitional and complete endocardial defects. Partial type includes primary type atrial septal defect and split mitral valve. In this type, the annulus of mitral valve and tricuspid valve is basically intact, but there are only small fissures, resulting in incomplete closure of mitral valve and reverse blood flow to the left atrium during left ventricular contraction, without combining septal defects. The transitional type includes a primary atrial diaphragm defect, a split mitral valve, and a smaller septal defect. The septal defect is located in the inflow tract portion of the ventricle, but the mitral and tricuspid valves are still separate at this time. The complete type has a primary atrial septal defect, a larger inflow tract interventricular diaphragm defect, and a common atrioventricular valve, which simply means that the doors of each of the two chambers do not have a door frame and have to be put together into a common channel that is incomplete in shape and function and has to function as its mitral and tricuspid valves. But the distribution of this common channel on the mitral and tricuspid valves is not necessarily uniform, and may be large on one side and small on the other. It is also possible that the tendon connecting the mitral valve bolts to the right ventricle, or more likely, that the right ventricle has no tendon at all in the left ventricle.