Diastolic movement of mitral valve in hypertrophic cardiomyopathy. An echocardiographic study.

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Abstract
Diastolic movement of the mitral valve and its relation to various aspects of left ventricular anatomy and function was investigated in 15 patients with hypertrophic cardiomyopathy. Echocardiograms showing left ventricular cavity and mitral valve simultaneously were recorded and subsequently digitized to obtain continuous plots of left ventricular dimension, its rate of change and peak diastolic closure rate of the anterior mitral valve leaflet. Septal and posterior wall thickness and left ventricular cavity and outflow tract dimension in mid-systole measured directly on the echocardiograms. All measurements were compared with those in 14 normal subjects. Patients with hypertrophic cardiomyopathy had smaller ventricles, with a conspicuous increase in septal thickness compared with those of normal subjects. Posterior wall thickness was only slightly increased, rapid filling period was normal; both the peak rate of increase of left ventricular dimension and the peak mitral diastolic closure rate were low. No relation between the 2 indices was found. Mitral valve closing velocity was strongly correlated with left ventricular outflow tract dimension. This relation was further validated by the infusion of isoprenaline, resulting in a simultaneous reduction of left ventricular outflow tract dimension and peak mitral closing velocity. In patients with hypertrophic cardiomyopathy, anatomical changes of the left ventricular outflow tract apparently are responsible for a disruption of the normal pattern of flow behind the anterior mitral valve leaflet, which results in a diminished closure rate of the valve in diastole.
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