The Diagnosis of Congenital Subaortic Stenosis

S URGICAL treatment of stenotic valvular lesions' requires definitive diagnosis. The clinical differentiation of aortic stenosis from congenital subaortic stenosis has always presented certain difficulties. Such factors as age of onset, history of rheumatic fever, and the quality of the second aortic heart sound have aided in the differentiation.2-5 Review of the literature indicates that subaortic stenosis is not rare. According to Abbott6 subaortic stenosis occurred as a primary lesion in 1.2 per cent of 1000 autopsied cases of congenital heart disease (as compared with an incidence of 9.2 per cent for patent ductus arteriosus). Since Chevers' original description of subaortic stenosis in 18427 numerous case reports of the lesion with and without associated anomalies have appeared.3 4, 8-17 The relative rarity of the isolated lesion at autopsy as compared with its clinical incidence suggests the benignity of subaortic stenosis. It is also probable that minor degrees are missed at autopsy. The congenital nature of the lesion described by Keith is generally accepted."8 19 Subaortic stenosis is analagous to infundibular stenosis in the right ventricle in that it probably represents an arrest of involution of the bulbus cordis. Usually a fibrous ridge or bar just below the semilunar valves extending 1 mm. to 1 cm. into the ventricular cavity, it consists of