Idiopathic Hypertrophy of the Interventricular Septum Causing Muscular Subaortic Stenosis in Children

Muscular subaortic stenosis due to ventricular septal hypertrophy has been recognized with increasing frequency in recent years. The literature deals chiefly with the condition in adults (1–9), reports of afflicted children being less numerous (10–13). Neufeld and his co-workers (10) discussed 2 cases, 1 in a still-born infant and the other in a one-month-old-child. In each a markedly thickened ventricular septum protruded into the out-flow tract of both ventricles, causing sub-pulmonary and subaortic stenosis. Wood and his associates (11), in their article on muscular subaortic stenosis in childhood, described the autopsy findings in 1 of their 3 cases. The left ventricular cavity was reduced to a slit by muscular hypertrophy of the left ventricle, and the interventricular septum was markedly thickened. The present series is intended to document 5 pediatric cases with evidence of ventricular septal hypertrophy and to show that the hypertrophy may affect the septum in a localized or a generalized fashion as well as by involving the ventricular wall. Material and Methods Five children presented with idiopathic hypertrophy of the interventricular septum causing muscular subaortic stenosis. Complete physical examinations were carried out, and conventional 12-lead electrocardiograms were obtained, plus 6 to 8 additional precordial leads as required to amplify the patterns presented. Radiographs of the chest were made in the anteroposterior, lateral, and right and left oblique positions in 4 children; in 1 (Case V) only an anteroposterior film was available, although fluoroscopy had been performed. All patients had heart catheterization: 3 combined right and left heart studies, 1 a right heart, and 1 a left heart catheterization. Selective angiography was performed with visualization of the left ventricle and aorta in Cases I to IV. The right side of the heart was outlined by the injection of contrast material into the right atrium in Case I and into the right ventricle in Case II. Films were obtained in the anteroposterior and lateral projections with an Elema Schönander film changer in 3 children, while in 1 (Case III) cineangiography was performed in the anteroposterior projection only. Further proof of diagnosis was obtained at surgery in 2 cases and at necropsy in 2. The 3 children who are alive are being followed regularly at the Cardiac Clinic of the Hospital for Sick Children (Toronto, Ont.) Classification Aortic stenosis may be classified as valvular, supravalvular, subvalvular, or muscular subaortic. It is not the purpose of this paper to discuss the first three conditions since they are reported in detail in a review by Peckham (14) of 276 cases at The Hospital for Sick Children. Subvalvular stenosis is usually considered to be due to a diaphragm or fibrous ring situated at a point 1 to 3 cm. below the aortic valve. The type of subaortic stenosis discussed in this paper is caused by muscular hypertrophy.