An unusual ventricular loop associated with right juxtaposition of the atrial appendages.

We report two autopsied cases of an unusual ventricular loop in hearts with right-sided juxtaposition of the atrial appendages. Case 1 showed usual atrial arrangement, a concordant atrioventricular connexion with a disharmonious ventricular loop showing left-hand topology and double outlet right ventricle with normally related arterial trunks. The atrioventricular connexions were crossing, with the inlet to the left-sided morphologically right ventricle being posterior to that of left ventricle. Mitral hypoplasia and coarctation of the aorta were the associated lesions. The second case showed usual atrial arrangement, a discordant atrioventricular connexion with an imperforate left atrioventricular orifice and double outlet right ventricle with the aorta in the right-sided position. A large right atrium was connected to right-sided morphologically left ventricle. A prominent dimple in the left atrial floor was firmly attached to the hypoplastic right ventricle which was left-sided and anterior. A small but discrete inlet portion of the right ventricle could be traced towards the anteriorly located left atrial dimple. Thus, despite the presence of a discordant atrioventricular connexion with the usual atrial arrangement, there was righ-hand ventricular topology. In each case the inlet component of the ventricular septum was displaced, being to the right in case 1 and anteriorly in case 2. We suggest that the embryologic mechanism producing disharmony between the atrioventricular connexion and the segmental combinations be interpreted on the basis of posterior ventricular looping, since they are best explained on the basis of a hypothetical heart with posteriorly located outflow tracts.