In the presence of a VSD, an aortic valve cusp (usually the right coronary cusp) may pro- lapse and partially or completely close the VSD, often with associated AR. At the time of VSD closure, aortic valve repair may be performed in an effort to stabilize or improve AR. For patients who meet GDMT criteria for aortic valve replace- ment, this may be performed concomitant with 3. In patients with unrepaired VSD, there is an increased risk of IE, typically involving the tricuspid and pulmonic valves. 4. Early attempts at surgical closure of nonrestric- tive VSD in patients with Eisenmenger syndrome were associated with an unacceptably high risk of mortality, and the practice was quickly abandoned. However, there are adult patients with large VSD and PAH who may benefit from closure of the VSD if the net shunt is left-to-right either at baseline or with PAH therapies. The use of fenestrated devices and fenestrated surgical patches in these patients leaves a small residual shunt to allow decompres- sion of the right heart.S4.1.3-5,S4.1.3-6 In theory, treat- ment of these patients with PAH therapies before closure could improve outcomes. 5. Closure of nonrestrictive VSD in adults with Eisenmenger syndrome who do not demonstrate left-to-right shunting and a decline in pulmo- nary vascular resistance with PAH therapies car- ries a high risk of mortality and should not be 4.1.4. Atrioventricular Septal Defect Recommendations for Atrioventricular Septal Defect Referenced studies that support recommendations are summarized in Online Data Supplement 29. COR LOE Recommendations Diagnostic IIa C-EO Cardiac catheterization can be useful in adults with atrioventricular septal defect when pulmonary hypertension is suspected. 