Anatomical variations on a univentricular circulation Anatomical variations on a univentricular circulation. a) Double inlet left ventricle (LV) with ventriculoarterial discordance and no pulmonary stenosis; b) tricuspid atresia with hypoplastic right ventricle (RV), ventriculoarterial concordance and hypoplas... Anatomical variations on a univentricular circulation. a) Double inlet left ventricle (LV) with ventriculoarterial discordance and no pulmonary stenosis; b) tricuspid atresia with hypoplastic right ventricle (RV), ventriculoarterial concordance and hypoplastic pulmonary artery (PA); and c) hypoplastic left heart syndrome with atrioventricular and ventriculoarterial concordance, hypoplastic left ventricle, aorta and aortic arch. Many classification systems have been proposed for univentricular hearts. The physician treating adult congenital heart disease needs an understanding of atrial arrangement, atrioventricular valve morphology and the morphology of the dominant ventricle, in addition to the surgical procedures that the patient has undergone, as all of these features will contribute to problems that may be faced in adult life. RPA: right pulmonary artery; LPA: left pulmonary artery; SVC: superior vena cava; RA: right atrium; LA: left atrium; PV: pulmonary vein; IVC: inferior vena cava; TV: tricuspid valve; MV: mitral valve. Paul Clift, and David Celermajer Eur Respir Rev 2016;25:438-450 ©2016 by European Respiratory Society