Atrial Septal Defect Recommendations for Atrial Septal Defect Referenced studies that support recommendations are summarized in Online Data Supplement 26 and the systematic review COR LOE Recommendations Diagnostic I C-EO Pulse oximetry at rest and during exercise is recommended for evaluation of adults with unrepaired or repaired ASD with residual shunt to determine the direction and magnitude of the shunt. I B-NR CMR, CCT, and/or TEE are useful to evaluate pulmonary venous connections in adults I B-NR Echocardiographic imaging is recommended to guide percutaneous Therapeutic I B-NRSR In adults with isolated secundum ASD causing impaired functional capacity, right atrial and/or RV enlargement, and net left- to-right shunt sufficiently large to cause physiological sequelae (eg, pulmonary systemic blood flow ratio [Qp:Qs] 1.5:1) without cyanosis at rest or during exercise, transcatheter or surgical closure to reduce RV volume and improve exercise tolerance is recommended, provided that systolic PA pressure is less than 50% of systolic systemic pressure and pulmonary vascular resistance is less than one third of the systemic vascular I B-NR Adults with primum ASD, sinus venosus defect or coronary sinus defect causing impaired functional capacity, right atrial and/ or RV enlargement and net left-to-right shunt sufficiently large to cause physiological sequelae (eg, Qp:Qs 1.5:1) without cyanosis at rest or during exercise, should be surgically repaired unless precluded by comorbidities, provided that systolic PA pressure is less than 50% of systemic pressure and pulmonary vascular resistance is less than one third of the systemic vascular resistance.S4.1.1-13,S4.1.1-14 Therapeutic (Continued) IIa C-LDSR In asymptomatic adults with isolated secundum ASD, right atrial and RV enlargement, and net left-to-right shunt sufficiently large to cause physiological sequelae (eg, Qp:Qs 1.5:1 or greater), without cyanosis at rest or during exercise, transcatheter or surgical closure is reasonable to reduce RV volume and/or improve functional capacity, provided that systolic PA pressure is less than 50% of systemic pressure and pulmonary vascular resistance is less than one third systemic resistance.S4.1.1-7 S4.1.1-10,S4.1.1-12 IIa C-LD Surgical closure of a secundum ASD in adults is reasonable when a concomitant surgical procedure is being performed and there is a net left-to-right shunt sufficiently large to cause physiological sequelae (eg, Qp:Qs 1.5:1 or greater) and right atrial and RV enlargement without cyanosis at rest or IIb B-NR Percutaneous or surgical closure may be considered for adults with ASD when net left-to-right shunt (Qp:Qs) is 1.5:1 or greater, PA systolic pressure is 50% or more of systemic arterial systolic pressure, and/or pulmonary vascular resistance is greater than one third of the systemic III: Harm C-LD ASD closure should not be performed in adults with PA systolic pressure greater than two thirds systemic, pulmonary vascular resistance greater than two thirds systemic, and/or a net right-to-left shunt.S4.1.1-21,S4.1.1-22 Synopsis ASDs are common and may occur as a consequence of different anatomic defects, including secundum ASD, primum ASD, sinus venosus defect (not properly a de- fect in the atrial septum but considered in this section), and coronary sinus septal defect. 