Pathophysiology and Natural History Congenital Heart Disease

The purpose of this study was to test the hypothesis that the presence of a subaortic ridge associated with a ventricular septal defect (VSD) is related to a malaligned ventricular septum caused by anterior or posterior deviation of the infundibular septum with or without obstructive lesions of the aortic arch. Thirty-two of 295 patients in whom a diagnosis of VSD was made by two-dimensional echocardiography and who were studied from June 1983 to Apnrl 1985 presented with a subaortic shelf. Every patient (p < .00001) had a malalignment type of defect; the defect was produced by anterior deviation of the outlet septumn (without compromise of the right ventricular outflow tract) in 28 and by posterior deviation of the infundibular septum in four. The prevalence of a subaortic shelf in the malalignment VSD group was 82% (32/39). Among the 28 patients with a subaortic ridge and anterior deviation of the outlet septum only three had aortic coarctation, but all four patients with subaortic stenosis and posterior infundibular malalignment had obstructive lesions of the aortic arch coarctation in three and interruption of the aortic arch in one (p < .00 1). We conclude that a malalignment type ofVSD may be a consistent feature in patients with VSD and associated discrete subaortic stenosis. We also noted a high prevalence of subaortic ridge in the presence of a malalignment VSD and therefore speculate that there may be a common morphogenesis for malalignment VSD, subaortic shelf, and obstructive lesions of the aortic arch. Circulation 75, No. 6, 1124-1129, 1987. THE EASY recognition and characterization of a "discrete" or fixed subaortic ridge by two-dimensional echocardiography now provides a method for the prospective study of the coexistence of ventricular septal defects (VSDs) and subaortic shelf.1-10 In the presence of a VSD, a subaortic stenosis may be clinically silent. Also, a subaortic shelf may not cause any gradient between the left ventricle and the aorta, but the obstruction can progress if the VSD is surgically or spontaneously closed.1' 13 The association of subaortic stenosis with VSDs has often been reported in the setting of aortic coarctation or interruption.'4 Furthermore, the morphologic type of VSD that is virtually always present in association with aortic coarctation or interruption is that of malalignment between the trabecular and infundibular septum (without right ventricular outflow tract obstruction), with aortic overriding, or as a result of posterior deviation of the outlet septum. 5' ` On the other hand, a From the Institute of Cardiology of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. Address for correspondence: Dr. Paulo Zielinsky, Instituto de Cardiologia do Rio Grande do Sul, Av. Princesa Isabel, 395, 90620 Porto Alegre RS Brazil. Received Nov. 7, 1985; revision accepted Feb. 12, 1987. 1124 malalignment VSD can also occur in the absence of coarctation or interruption of the aortic arch. This study was carried out to test the hypothesis that the presence of a subaortic ridge associated with a VSD is related to a malaligned ventricular septum caused by anterior or posterior deviation of the infundibular septum with or without obstructive lesions of the aortic arch.