Patent ductus arteriosus (PDA). This defect, which normally occurs during fetal life, short circuits the normal pulmonary vascular system and allows blood to mix between the pulmonary artery and the aorta. Prior to birth, there is an open passageway between the two blood vessels, which closes soon after birth. When it does not close, some blood returns to the lungs. Patent ductus arteriosus is often seen in premature infants.
Atrioventricular canal (AVC or AV canal). Atrioventricular canal is a complex heart problem that involves several abnormalities of structures inside the heart, including atrial septal defect, ventricular septal defect, and improperly formed mitral and/or tricuspid valves.
Hypoplastic left heart syndrome (HLHS). A combination of several abnormalities of the heart and the great blood vessels. In hypoplastic left heart syndrome, most of the structures on the left side of the heart (including the left ventricle, mitral valve, aorta, and aortic valve) are small and underdeveloped. The degree of underdevelopment differs. The functional ability of the left ventricle can be reduced to the extent of not being able to pump an adequate blood volume to the body. Hypoplastic left heart syndrome can be fatal without treatment.
Pulmonary atresia. A complicated congenital defect in which there is abnormal development of the pulmonary valve. Normallythe pulmonary valve is found between the right ventricle and the pulmonary artery. It has three leaflets that function like a one-way door, allowing blood to flow forward into the pulmonary artery, but not backward into the right ventricle.
With pulmonary atresia, problems with valve development prevent the leaflets from opening, therefore, blood cannot flow forward from the right ventricle to the lungs.
Double outlet right ventricle (DORV). A congenital heart defect (one that occurs as the heart is forming during pregnancy) in which both the aorta and the pulmonary artery are connected to the right ventricle.
Truncus arteriosus. The aorta and pulmonary artery start as a single blood vessel, which eventually divides and becomes two separate arteries. Truncus arteriosus occurs when the single great vessel fails to separate completely, leaving a connection between the aorta and pulmonary artery.
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