ABNORMALITIES OF THE LEFT-VENTRICULAR OUTFLOW TRACT ASSOCIATED WITH DISCRETE SUBAORTIC STENOSIS IN CHILDREN - AN ECHOCARDIOGRAPHIC STUDY

Objectives. The purpose of this study was to examine the echocardiogra phic abnormalities of the left ventricular outflow tract associated wi th subaortic stenosis in children. Background. Considerable evidence s uggests that subaortic stenosis is an acquired and progressive lesion, but the etiology remains unknown. We have proposed a four-stage etiol ogic process for the development of subaortic stenosis. This report ad dresses the first stage by defining the morphologic abnormalities of t he left ventricular outflow tract present in patients who develop suba ortic stenosis. Methods. Two study groups were evaluated-33 patients w ith isolated subaortic stenosis and 12 patients with perimembranous ve ntricular septal defect and subaortic stenosis-and were compared,vith a size- and lesion-matched control group. Subjects ranged in age from 0.05 to 23 years, and body surface area ranged from 0.17 to 2.3 m(2). Two independent observers measured aortoseptal angle, aortic annulus d iameter and mitral-aortic separation from previously recorded echocard iographic studies. Results. The aortoseptal angle was steeper in patie nts with isolated subaortic stenosis than in control subjects (p < 0.0 01). This pattern was also true for patients with ventricular septal d efect and subaortic stenosis compared with control subjects (p < 0.001 ). Neither age nor body surface area was correlated with aortoseptal a ngle. A trend toward smaller aortic annulus diameter indexed to patien t size was seen between patients and control subjects put failed to ac hieve statistical significance (p = 0.08). There was an excellent inte rrater correlation in aortoseptal angle and aortic annulus measurement . The mitral-aortic separation measurement was unreliable. Our results , specifically relating steep aortoseptal angle to subaortic stenosis, confirm the results of other investigators. Conclusions. This study d emonstrates that subaortic stenosis is associated with a steepened aor toseptal angle, as defined by two-dimensional echocardiography, and th is association holds in patients with and without a ventricular septal defect. A steepened aortoseptal angle may be a risk factor for the de velopment of subaortic stenosis. (C) 1997 by the American College of C ardiology.