Atrial Septal Defect

Types

Ostium Secundum Atrial Septal Defect

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Ostium secundum ASD is the most common type of ASD. It occurs in the center of the septum between the right and left atrium. A variant of this type of ASD is called a patent foramen ovale (PFO) and is very small.

Ostium Primum Atrial Septal Defect

Ostium primum is the next most common type and is located in the lower portion of the atrial septum. This type of ASD often will have a mitral valve defect associated with it called a mitral valve cleft. A mitral valve cleft is a slit-like or elongated hole in one of the leaflets (anterior leaflet) that form the mitral valve.

Sinus Venosus Atrial Septal Defect

A sinus venosus defect is the least common type of ASD and is located in the upper portion of the atrial septum. A sinus venosus ASD often has an abnormal pulmonary vein connection associated with it. Four pulmonary veins, two from the right lung and two from the left lung, normally return red blood to the left atrium. Usually with a sinus venosus ASD, a pulmonary vein from the right lung will be abnormally connected to the right atrium instead of the left atrium. This is called an anomalous pulmonary vein.