Patent ductus arteriosus (PDA) is a condition in which the ductus arteriosus does not close. The word "patent" means open. The ductus arteriosus is a blood vessel that allows blood to go around the baby's lungs before birth. Soon after the infant is born and the lungs fill with air, the ductus arteriosus is no longer needed. It usually closes in a couple of days after birth. If the vessel doesn't close, it is referred to as a PDA. PDA leads to abnormal blood flow between the aorta and pulmonary artery, two major blood vessels that carry blood from the heart.
Atrial septal defect (ASD) is a heart defect that is present at birth (congenital). As a baby develops in the womb, a wall (called the interatrial septum) forms that divides the upper chamber into a left and right atrium. An abnormal formation of this wall can result in a hole that remains after birth. This is called an atrial septal defect, or ASD.
Ventricular septal defect is a hole in the wall that separates the right and left ventricles of the heart. Ventricular septal defect is one of the most common congenital (present from birth) heart defects. It may occur by itself or with other congenital diseases.
Tetralogy (teh-TRAL-o-je) of Fallot (fah-LO) is a congenital heart defect. This is a problem with the heart's structure that's present at birth. Congenital heart defects change the normal flow of blood through the heart. Tetralogy of Fallot is a rare, complex heart defect. It occurs in about 5 out of every 10,000 babies. The defect affects boys and girls equally.
Transposition of the great vessels is a heart defect that occurs from birth (congenital). The two major vessels that carry blood away from the heart -- the aorta and the pulmonary artery -- are switched (transposed).