there is absence of the left atrioventricular connection and the right atrium is connected to a dominant left ventricle When there is atresia of the left atrioventricular valve or absence of the left atrioventricular connection with the right atrium connected to a dominant right ventricle and the ventricular septum is intact, such hearts will form part of the hypoplastic left heart syndrome (see earlier) The aorta is usually atretic or else critically stenotic In the setting of deficient ventricular septation, the arrangement is described in terms of mitral atresia with patent aortic root, often with a double outlet from the right ventricle Irrespective of the anatomic combinations, the surgical option is likely to be conversion to the Fontan circulation The described heterogeneity points to the need, in each case, for full sequential segmental analysis FIG 69.14 Anatomic substrates for atrioventricular valvar atresia Left, Imperforate tricuspid valve in the setting of concordant atrioventricular connections Right, Absence of the right atrioventricular (RAV) connection in a heart with classic tricuspid atresia Both arrangements are functionally univentricular, but the heart at left has biventricular atrioventricular connections FIG 69.15 Anatomic substrates for mitral atresia in the setting of the right atrium connected to the morphologically right ventricle (A) Concordant connections, and the atresia is produced by an imperforate mitral valve (B) Complete absence of the left atrioventricular (LAV) connection in the setting of the hypoplastic left heart syndrome The incomplete left ventricle is slitlike FIG 69.16 Typical features of the most common variant of tricuspid atresia Left, Morphology of the right atrium As shown in Fig 69.4, the dimple overlies the atrioventricular component of the membranous septum Right, Right ventricle, which is incomplete because it totally lacks its inlet component The heart shown has concordant ventriculoarterial connections, with a long infundibulum leading to the pulmonary trunk The infundibulum is much shorter when the ventriculoarterial connections are discordant VSD, Ventricular septal defect