Ventricular Systolic Septal Thickening and Excursion in Idiopathic Hypertrophic Subaortic Stenosis

Asymmetric septal hypertrophy has been described as the pathognomonic abnormality in idiopathic hypertrophic subaortic stenosis. It has been suggested that the ventricular septum is hypercontractile and accounts for the left ventricular outflow-tract obstruction. Twenty-nine patients with idiopathic hypertrophic subaortic stenosis were studied by cardiac ultrasound to determine the degree of systolic thickening and amplitude of excursion of the ventricular septum. In all patients septal thickening was significantly reduced from normal, with a range of 0 to 22 per cent (mean of 9.3 per cent). The excursion of the left ventricular septal echo ranged from 1 to 6 mm (mean of 4 mm) and was decreased from normal in 21 patients. Therefore, the septum does not appear to be a hypercontractile structure in this disorder. These results take issue with previously proposed pathophysiology and suggest that other hypotheses need further investigation. (N Engl J Med 291:1317–1319, 1974)