Outcomes and questions about discrete subaortic stenosis.

D iscrete subaortic stenosis (DSS) is a well-described cause of isolated left ventricular outflow tract (LVOT) obstruction in children. 1 The lesion is of obvious hemodynamic significance , but in addition, it is recognized to be the result of a dynamic process that continues and has consequences into adulthood. Consequently, there are questions (including the mechanism of formation, the surgical approaches, the implications for the aortic and mitral valves, and its natural history , as well as the likelihood of recurrence) the answers to which are important to the understanding and treatment of DSS. Despite the many reports on DSS, none of these related questions have been answered completely. The report on surgical outcome of discrete subaortic stenosis in adults by van der Linde et al 2 in the March 19, 2013, issue of Circulation, however, adds useful information on the latter questions. This report and others in the literature indicate DSS, even after an apparently successful surgical resection, is a lesion that does not go away easily. DSS in its discrete form, without a tubular obstruction of the LVOT, is fairly uniform in appearance. 3 For the surgeon, the resection of a DSS is both a " nice case " and one that may prove to be dismaying in the future. DSS is often an essentially circular fibromuscular rim of tissue, with a fibrous inner ring of varying width. The location will vary from just beneath the aortic valve, where occasionally it will be fused with the dependent portion of a cusp, to a position lower down the LVOT with attachments to the anterior leaflet of the mitral valve. This location means that not only will it place a load on the left ventricle (LV), but the resulting turbulence will also affect the aortic valve downstream. The mechanism for DSS formation has been the subject of debate since its original description. Despite being generally classified as a congenital heart defect and, on rare occasion, appearing in infancy, the general opinion is that DSS is an acquired lesion. 1 There have only been rare reports suggesting a familial occurrence, and overall, there is little evidence that it is a primarily genetic disorder. 4 Although a developmental origin has the most support, it does not appear to completely explain these lesions, and questions remain. The inciting anatomy and the beginning events may be quite subtle, and early childhood cases have been …