[Sigmoid septum causing left ventricular outflow tract obstruction: a case report].

A 67-year-old man with a sigmoid septum causing the left ventricular outflow obstruction by inotropic stimulation was reported. This patient was admitted to the Hospital of the University of Tsukuba because of chest pain. Phonocardiography revealed a systolic ejection murmur which was intensified by amyl nitrite inhalation. A carotid pulse tracing showed a mid-systolic dip and a secondary slow wave during amyl nitrite inhalation. M-mode echocardiography demonstrated neither systolic anterior motion of the mitral valve (SAM) nor mid-systolic closure of the aortic valve at rest. Two-dimensional echocardiography revealed a basal interventricular septum markedly protruding into the left ventricle (sigmoid septum). The remainder of the septum and the left ventricular free wall were not hypertrophied, and no enlargement of the left ventricular cavity was observed. During exercise tests, blood pressure dropped significantly. Cardiac catheterization showed a pressure gradient within the left ventricle with isoproterenol infusion and post-extrasystolic potentiation. These findings suggest that left ventricular outflow tract obstruction could occur in a patient with sigmoid septum by inotropic stimulation, producing a fall of blood pressure during exercise.