Correlation of distance from subaortic membrane to base of the right aortic valve cusp and the development of aortic regurgitation in mild discrete subaortic stenosis

Discrete subaortic stenosis (DSS) is an uncommon congenital cardiac anomaly in which the left ventricular outflow tract is narrowed by either a fibrous membrane, a muscular ridge or a fibromuscular tunnel, either singly or in various combinations.¹ The most common type of DSS involves the subaortic membrane. The anomaly is hazardous, not only because of obstruction and hemodynamic impairment, but also because of its complications,^1-5 including aortic regurgitation (AR), infective endocarditis and possible development of an inherently associated muscular obstruction. Aortic regurgitation is the most frequent complication, observed in up to 50% of affected patients.^1-7 Most series of DSS patients include mainly those with moderate to severe obstruction. However, the detection and management of DSS have improved due to echocardiography,⁸ and patients with only mild obstruction are diagnosed more often. In a recent study,⁹ we observed that even patients with mild DSS (peak pressure gradient <40 mm Hg) can develop complications, as 10 from a group of 21 patients had AR. Because early surgery is the only way to prevent such a complication, a method of predicting high risk patients is desirable. In the present study we attempted to identify patients with mild DSS who will develop AR on the basis of the distance between the membrane and the aortic valve.