The ASD most commonly associated with mitral insufficiency is:

C. Ostium primum defect.

DISCUSSION: Ostium primum defects, or “partial” AV canal defects, are commonly associated with a “cleft” of the anterior leaflet of the mitral valve. Depending on the deformity of the mitral valve, these defects can be accompanied by variable degrees of mitral insufficiency. This cleft of the mitral valve needs to be repaired at the same time that the defect is closed. Although other types of ASDs can be associated with mitral insufficiency, this is not as common. When mitral stenosis exists with a secundum ASD the condition is often referred to as Lutembacher's syndrome.