Natural history of growth of secundum atrial septal defects and implications for transcatheter closure

To investigate the natural history of secundum atrial septal defects (ASDs) over several years using serial echocardiographic studies.

All patients with isolated secundum ASDs who had serial transthoracic echocardiograms at Texas Children's Hospital, Houston, Texas, from January 1991 to December 1998 were identified. Patients with fenestrated or multiple ASDs, other congenital heart defects, or less than a six month interval between echocardiograms were excluded. There were 104 patients eligible for inclusion in the study. Studies were reviewed by two echocardiographers (blinded) and the maximal diameter was recorded. Defects were defined as small (> 3 mm to < 6 mm), moderate (> or = 6 mm to < 12 mm), or large (> or = 12 mm). ASDs that grew > or = 20 mm were defined as having outgrown transcatheter closure with the device available to the authors' institution.

ASD diameter increased in 68 of 104 patients (65%), including 31 patients (30%) with a > 50% increase in diameter. Spontaneous closure occurred in four patients (4%). Thirteen defects (12%) increased to > or = 20 mm. One fifth of the patients studied had an insufficient atrial rim by transthoracic echocardiogram to hold an atrial septal occluder. The only factor associated with significant growth of ASDs was initial size of the defect. ASD growth was independent both of age at diagnosis and when indexed to body surface area.

Two thirds of secundum ASDs may enlarge with time and there is the potential for secundum ASDs to outgrow transcatheter closure with specific devices. Further development in devices and general availability of devices capable of closing larger ASDs should circumvent this problem.