Circulation
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Dynamic obstruction to left ventricular outflow in patients with hypertrophic cardiomyopathy usually occurs when the anterior mitral leaflet moves forward in systole and approaches or contacts the ventricular septum. However, we have recently identified, by M mode and two-dimensional echocardiography, 21 patients with hypertrophic cardiomyopathy who had a unique pattern of mitral valve motion characterized by abnormal mitral valve coaptation and systolic anterior motion of the posterior mitral leaflet. This abnormality of mitral valve motion was most reliably identified with two-dimensional echocardiography in views of the left ventricle obtained from the apex. ⋯ Of the 16 patients who underwent cardiac catheterization, nine had basal subaortic gradients of 20 to 85 mm Hg, which were apparently due to moderate or marked systolic anterior motion of the posterior mitral leaflet. Ventricular septal myotomy-myectomies were performed in two patients and resulted in markedly diminished systolic anterior motion of the posterior mitral leaflet in each and abolition of subaortic gradient in the one patient who underwent postoperative cardiac catheterization. Hence, in patients with hypertrophic cardiomyopathy, systolic anterior motion of the posterior mitral leaflet (1) is not uncommon (identifiable in about 10% of a consecutively studied series of patients), (2) constitutes a previously undescribed mechanism for dynamic subaortic obstruction, and (3) is due to a malformation of the posterior mitral leaflet.