Intramural VSD is a type of residual VSD seen after repair of complex defects like double outlet right ventricle, truncus arteriosus or Rastelli procedure for transposition of great arteries. The intramural VSD originates between the insertion of the VSD closure patch and the aortic valve. The defect occurs because of coarse trabeculae of the hypertrophic right ventricle prevent good seal at the site of patch insertion so that blood can tunnel through the trabeculae from the left ventricular outflow tract into the right ventricle through its wall (intramural). Due to the peculiar location, it is often difficult to image intramural VSDs properly, both by transthoracic and transesophageal echocardiography. High parasternal views on trans thoracic and deep trans gastric views on trans esophageal echocardiography are often needed for delineation of the intramural VSDs. The defects can increase in size over time and more shunt can be established.
These shunts may be difficult to eliminate by surgical repair and contribute to morbidity and mortality after the repair of conotruncal anomalies. A recent study published in Circulation  confirmed that intramural VSDs in addition prolong the postoperative hospital stay and need for ECMO (Extracorporeal membrane oxygenator). In their series of over four hundred and forty subjects, over half had residual VSDs, of which forty nine (11%) had intramural VSDs. Since these VSDs are not accessible through atriotomy or right ventriculotomy, transaortic closure has been advocated .