Ventricular Septal Defect Recommendations for Ventricular Septal Defect Referenced studies that support recommendations are summarized in Online Data Supplement 28. COR LOE Recommendations Therapeutic I B-NR Adults with a VSD and evidence of left ventricular volume overload and hemodynamically significant shunts (Qp:Qs 1.5:1) should undergo VSD closure, if PA systolic pressure is less than 50% systemic and pulmonary vascular resistance is less than one third systemic.S4.1.3-1 IIa C-LD Surgical closure of perimembranous or supracristal VSD is reasonable in adults when there is worsening aortic regurgitation (AR) caused by VSD.S4.1.3-1,S4.1.3-2 IIb C-LD Surgical closure of a VSD may be reasonable in adults with a history of IE caused by VSD if not otherwise contraindicated.S4.1.3-3 IIb C-LD Closure of a VSD may be considered in the presence of a net left-to-right shunt (Qp:Qs 1.5:1) when PA systolic pressure is 50% or more than systemic and/or pulmonary vascular resistance is greater than one third III: Harm C-LD VSD closure should not be performed in adults with severe PAH with PA systolic pressure greater than two thirds systemic, pulmonary vascular resistance greater than two thirds systemic and/or a net right-to-left Synopsis Ventricular septal defects (VSDs) initially create a vol- ume load to the left heart, and the magnitude of he- modynamic impact is directly related to the size of the shunt and afterload to the ventricles. Isolated VSDs are the most commonly encountered form of CHD in the Most isolated mus- CLINICAL STATEMENTS AND GUIDELINES cular and perimembranous VSDs are small and close spontaneously. The spectrum of isolated residual VSDs encountered in the adult patient includes: 1. Small restrictive defects. The pulmonary vascular resistance is not significantly elevated and the left-to-right shunt is small (Qp:Qs <1.5:1). 2. 