Levo-transposition of the great arteries is a complex cardiac defect. In this condition, the lower portion of the heart is fully reversed. Normally, the lower portion of the heart consists of two chambers and two arteries, one to connect to each chamber. One artery is responsible for transport of oxygen-poor blood to the lungs, and the other for transport of oxygen-rich blood to the body. L-transposition of the great arteries means that the position of the two chambers is reversed, and the position of the two arteries is also reversed. This ‘double reversal’ makes this condition less dangerous than others because the lungs can still receive oxygen-poor blood and the body still gets oxygen-rich blood. The causes of this condition are unknown, but babies born with this condition usually do not have a blue-tinted skin like in dextro-transposition of the great arteries or other cardiac defects. L-transposition of the great arteries might be not detected until later in life when congestive heart failure, heart murmurs, and abnormal heart rhythms may develop. Treatment may not be needed unless there are other complications or heart defects.