Ventricular Septal Defect Justin T Tretter, Lee Benson, Adrian Crucean, Diane E Spicer, Robert H Anderson Abstract Ventricular septal defects are among the most common forms of congenital heart disease, yet there remains contention regarding their description In congruence with the newly proposed ICD-11 codes, we propose an approach that identifies the borders of the defect, with further subclassification according to their right ventricular geography and the presence or absence of septal malalignment This simple approach identifies three major categories: perimembranous, doubly committed and juxtaarterial, and muscular ventricular septal defects This approach is in line with the developmental aberrations underlying these malformations, is objectively defined by echocardiography, and—of more clinical relevance —directly relates them to the location of the atrioventricular conduction system This chapter highlights the morphology and morphogenesis of these various subtypes of ventricular septal defects We further describe their pathophysiology, resulting clinical features, imaging assessment and diagnosis, clinical course and prognosis, and management, including that of surgical repair and interventional closure as well as the subsequent outcomes Keywords Interventricular communications; Ventricular septum; Development; Surgical treatment; Interventional closure Introduction Holes between the ventricles can occur as isolated anomalies but are also seen in association with many other defects For example, they are found as integral parts of entities such as the tetralogy of Fallot, double-outlet ventricles, and most cases of common arterial trunk They are also frequently encountered in association with transposition and congenitally corrected transposition Although fundamentally different from ventricular septal defects, atrioventricular septal defects also commonly have a ventricular component (see Chapter 31) Ventricular septal defects, furthermore, are an integral part of the functionally univentricular circulation Taken together, they unequivocally make up the commonest congenital cardiac malformation This chapter considers only the “isolated” examples, although complications produced by other minor associations are discussed Although holes between the ventricles have a long pedigree, it is with the name of Henri-Louis Roger1 that the anomaly is historically linked Roger recognized that an isolated ventricular septal defect produced a typical murmur and that it could be consistent with prolonged life and good health