Surgical correction in mirror-image atrial arrangement or left atrial isomerism with systemic venous return to the left-sided atrium.

We have recently encountered three patients with the hemodynamics of complete transposition accompanied by unusual atrial arrangements. The flow patterns produced all required correction by means of a "mirror-image" Mustard operation. Two of the patients had left atrial isomerism as evidenced by the finding of bilateral atrial appendages of morphologically left type. In both patients the systemic venous return was to the left-sided atrium and the pulmonary venous return to the right-sided atrium. The major effect of the isomerism was to reduce the volume of the left-sided chamber. This initially produced concern, since we now try to avoid enlargement of the pulmonary venous atrium when performing Mustard's operation. However, despite the small volume, it was possible to place the baffle without producing postoperative pulmonary or systemic venous obstruction. The other significant effect of left atrial isomerism is to deviate the position of the sinus node, but thus far we have not encountered any postoperative rhythm problems. The third patient had a mirror-image arrangement of the atrial chambers and the venous connections (situs inversus), and the anatomy was corrected by straightforward mirror-image reversal of our current technique for Mustard's procedure.