Anomalous coronary artery (ACA) is a congenital (present at birth) heart defect that happens when the blood vessels that carry oxygen-rich blood to the heart are abnormal. This could mean they have an unusual shape or size, or they may even be in the wrong location. These different types of ACAs are hard to diagnose because they may not even cause symptoms. Once symptoms begin, it takes experience to identify coronary artery anomalies