Uhl anomaly		Congenital malformation consisting of nearly total absence of the right ventricular myocardium, presenting with marked enlargement of both the right ventricle and right atrium and subsequent tricuspid regurgitation. Arrhythmogenic right ventricular dysplasia may be one end of a spectrum and Uhl anomaly the other.
unbalanced A-V canal		see ventricular imbalance.
unifocalization		A surgical technique that creates a common trunk for multiple direct aorto-pulmonary collateral arteries, as part of the surgical management of complex pulmonary atresia.
univentricular connection		Both atria are connected to only one ventricle. The connection is univentricular, but the heart is usually biventricular.
unroofed coronary sinus		An anomaly in which there is a deficiency in the normal separation of the coronary sinus from the left atrium as the coronary sinus passes behind the LA in the A-V groove, such that the coronary sinus drains into the LA. A form of absence of the coronary sinus.
upstairs-downstairs heart		see supero-inferior heart