THE RELATIONSHIP OF THE OUTLET SEPTUM TO THE AORTIC OUTFLOW TRACT IN HEARTS WITH INTERRUPTION OF THE AORTIC-ARCH

We examined 13 hearts with concordant atrioventricular and ventriculoarterial connections and interruption of the aortic arch to establish and describe the morphologic features of the outflow tracts in relation to axial deviation and malalignment of the outlet septum as opposed to overriding of the arterial valvular orifices. Interruption in all cases but one was between the left common carotid and left subclavian arteries; the other arch was interrupted at the isthmus, A patent arterial duct and ventricular septal defect were universally present. When its borders were viewed from the right ventricle, the ventricular septal defect was perimembranous in seven hearts, had exclusively muscular borders in four hearts, and was doubly committed and juxta-arterial in the remaining two hearts, Malalignment between the muscular ventricular septum and outlet septum, or a fibrous raphe, as judged when the heart was viewed in its short axis, was found in 12 of the hearts. Posterior and leftward axial deviation of the outlet septum in its long axis was found in 4 of the 12 hearts and also in one heart that did not have short-axis malalignment. Attachments of the leaflets of the pulmonary valve in both right and left ventricles, however, were present in only one of the specimens, this being a case with a doubly committed and juxta-arterial defect. These separate features of the outflow tract in hearts with interruption of the aortic arch, therefore, require thorough assessment when surgical management is planned. All these variable features can be assessed preoperatively by cross-sectional echocardiography, which should be directed toward defining the degree of development and alignment of the outlet septum, as well as the length of the subpulmonary infundibulum.