This diagram depicts a ventricular septal defect (VSD) in the membranous septum. There is a left-to-right shunt, the severity of which depends upon the size of the defect. VSD's may also occur in the muscular septum and may be multiple. Over time, about half will close spontaneously. Persons with VSD's (as with most cardiac defects) are at greater risk for infective endocarditis.