Absence of one atrioventricular connection associated with straddling atrioventricular valve: distinction of a solitary from a common valve and further considerations on the diagnosis of ventricular topology.

Hearts with absence of the right atrioventricular connection (tricuspid atresia) are rarely associated with straddling of the left atrioventricular valve. We describe two hearts in which the left atrium is connected mostly to a dominant left ventricle but, in part, to a rudimentary right ventricle. In these particular hearts, this arrangement caused major problems in determining ventricular topology. This feature, the so-called handedness of the ventricular mass, is determined in hearts with two complete ventricles by attempting to place the palm of one's hand on the right ventricular septal surface with the thumb in the inlet and the fingers pointing to the outlet. The problems in these two cases were produced because the rudimentary right ventricle had only part of an inlet component. The discerned pattern of topology was different in the two cases, being left hand in one and right hand in the other. These cases emphasize, first, the need to distinguish between ventricular topology and the atrioventricular connection and, second, between a solitary and a common atrioventricular valve when the valvar tension apparatus is straddling.