An echocardiographic study of localized subaortic hypertrophy

A prospective echocardiographic investigation was undertaken to determine the prevalence and significance of localized subaortic hypertrophy in WOO consecutive patients presenting for a routine echocardiographic examination. Localized septal hypertrophy was diagnosed when the subaortic septum was hypertrophied ( 2 SD from normal) with a normal size cavity due to aortic valve disease (2 patients were also hypertensive). Of the 180 patients with aortic valve disease, localized subaortic hypertrophy was found in 10% of those with left ventricular hypertrophy and 33% of those with asymmetrical-septal hypertrophy (septum to posterior wall ratio of >l.5:1). There was no evidence of subaortic stenosis by pulsed and continuous wave doppler echocardiography (8 cases) and cardiac catheterization (6 cases). The aetiology of this discrete localized muscular bulge is unclear but is presumably due to change in shape of the septum with left ventricular hypertrophy. However, this finding has important implications as a cause of asymmetrical septal hypertrophy and because of the possible false diagnosis of subvalvular stenosis and its effect on ultrasound measurements.