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Epidemiology
Atrial septal defects (ASDs) are among the most common cardiac malformations, with prevalence [including persistence of patent foramen ovale (PFO)] greater than 15 percent for the general population and, when other cardiac anomalies are present, as high as 35 to 50 percent, with slight female predominance.
Morphology
Atrial septal defects can be categorized according to the area of deficient interatrial septum: Secundum-type/PFO (most common), superior/inferior sinus venosus (SV), primum defects, coronary sinus (CoS) ASDs. Partial anomalous pulmonary venous connection (PAPVC) and scimitar syndrome often occur in the setting of an ASD. Defects are variable in size: from restrictive, to unrestrictive, to virtual absence of any septal rim.
Pathophysiology
Magnitude of left-to-right shunt depends on the respective compliance of right and left ventricles and on the diameter of the defect. Because of streaming of systemic venous return toward the LA, superior and inferior SV defects can present with mild cyanosis. A minority of patients with very large defects will develop pulmonary venous obstructive disease over several decades and, eventually, fixed pulmonary hypertension (PHTn) and right-to-left shunting.
Clinical features
In the absence of other malformations, ASDs are rarely symptomatic in early infancy. Features of pulmonary overcirculation (dyspnea, failure to thrive, recurrent respiratory infections) are rare in early childhood. Arrhythmias or paradoxical emboli can be initial modes of presentation.
Diagnosis
Physical exam (split and fixed second heart sound) and chest x-ray (CXR) (cardiomegaly, anomalous vascular markings in PAPVC) suggest the diagnosis, confirmed by transthoracic echocardiography (TTE). In equivocal cases and for PAPVC/scimitar syndrome (SS), transesophageal echocardiography (TEE), magnetic resonance imaging (MRI), and computed tomography (CT) might be utilized. Cardiac catheterization has almost no role in the diagnostic workup, except for patients with evidence of PHTn considered for surgical closure.
Treatment
Surgical closure is rarely indicated in infancy, but should be performed for unrestrictive defects in preschool age and for symptomatic adults and cases of paradoxical embolization. When the anatomy is permissive, percutaneous device closure can be considered. Conventional primary or patch closure of the defect can be accomplished via a right thoracotomy or limited/full sternotomy and, in the current era, should be associated with virtually no mortality or significant morbidity.
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We define an atrial septal defect (ASD) as a deficiency of any size in the atrial septum (Fig. 64-1). Although briefly mentioned in this chapter, we will not include among ASDs the patent foramen ovale (PFO); this flap-valve is bordered superiorly by the upper limbic tissue and inferiorly by the valve of the fossa ovalis, which opens only in specific circumstances, as during coughing or the Valsalva maneuver. The ostium primum (OP) defect is part of the spectrum of atrioventricular septal defects (AVSDs) and is discussed in detail in Chapter 66.
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