What is a hallmark finding of transposition of the great arteries on the three-vessel/trachea view?

• A. The great arteries show the normal spiral/serial relation
• B. There is a single great artery trunk
• C. Arteries cross over in a typical spiral relation
• D. The great arteries arise side-by-side with abnormal parallel arrangement

Answer: (D)

In the three-vessel/trachea view, the key is how the great arteries relate to each other. In a normal heart, the arteries cross in a spiral fashion as they arise from the ventricles. In transposition of the great arteries, the two great arteries run side-by-side in a parallel arrangement rather than spiraling around each other. This parallel, abnormal orientation occurs because the aorta comes from the right ventricle and the pulmonary artery from the left ventricle. So, the hallmark finding is the great arteries arising side-by-side with a parallel arrangement. The other patterns describe normal spiral crossing, a single trunk, or a typical spiral relation, which do not fit transposition.