An echocardiographic study of the association of ventricular septal defect and right ventricular muscle bundles with a fixed subaortic abnormality.

Since 1983, 36 patients with the combination of right ventricular muscle bundles and a perimembranous ventricular septal defect have been studied in our institution to address the incidence of on associated subaortic abnormality. Of that total 32 (88%) had echocardiographic evidence of such an abnormality (29 had a typical subarotic ridge protruding from the crest of the interventricular septum and the remaining 3 had an echodense area in the same location). Surgical confirmation of the presence or absence of a subaortic abnormality was available in 26. There was correlation between the surgical and echocardiographic findings in all patients. A resting Doppler gradient of greater than or equal to 10 mm Hg was present in only 10. During the study period, 6 patients had Doppler evidence of progression of their gradient. The incidence of subaortic abnormalities in right ventricular muscle bundles and ventricular septal defects appears to be far greater than previously suspected. The exact significance of this finding in the absence of a pressure gradient is still unclear.