The foramen ovale is a hole in the wall between the left and right atria of every human fetus. This hole allows blood to bypass the fetal lungs.Patent ductus arteriosus (PDA) is a persistent opening between the two major blood vessels leading from the heart. The following billing and coding guidance is to be used with its associated Local Coverage Determination. The ductus arteriosus is a hole that allows the blood to skip the circulation to the lungs. Carotid stenosis is a narrowing of the carotid arteries, the two major arteries that carry oxygen-rich blood from the heart to the brain. The purpose of this guide is to provide you with basic information about filing a utility patent application with the USPTO. Intracranial stenosis is the severe narrowing of an artery within the skull. A blood vessel narrows when fatty deposits (plaque) build up inside the vessel. Aortic valve stenosis is a serious type of congenital heart defect.