Standing position alone or in combination with exercise as a stress test to provoke left ventricular outflow tract gradient in hypertrophic cardiomyopathy and other conditions.

Measuring left ventricular outflow tract (LVOT) gradient by echocardiography in decubitus position, which is used in routine clinical practice, does not reflect the pathophysiology of this dynamic abnormality during daily activities, which trigger the symptoms. LVOT obstruction is dynamic and greatly dependent upon the left ventricular cavity size, geometric configuration of hypertrophy, load, contractility and mitral apparatus abnormalities, including systolic anterior motion of mitral leaflet. Importantly, LVOT gradient may develop not only in hypertrophic cardiomyopathy, but also in other heart diseases. Recent studies show that LVOT gradient should be measured both in a standing position and during exercise.