Transmitral Doppler indices
Key variables to be considered during echocardiographic evaluation of diastolic dysfunction include early diastolic transmitral velocity (E), early diastolic mitral annular velocity by tissue Doppler imaging (TDI) (e’) and their corresponding relationship (E/e’), LA volume index (LAVi) and peak tricuspid regurgitation velocity.40 In the setting of MS, however, these offer limited value to assess myocardial disease as they are often related to the degree of valvular stenosis. E-wave velocity reflects left-sided atrioventricular gradient during early diastole and is affected by alterations in LV relaxation and LA pressure. In the setting of significant LV diastolic dysfunction, transmitral gradient is low despite increased LA pressure owing to concomitant increase in LV diastolic pressure. Pressure half-time employing echocardiography, thereby, is decreased due to increase in LV diastolic pressure caused by increased LV chamber stiffness and hence, may not provide an accurate estimation of valve area using this method.40 (Figures – 1, 2). Further, elevated transmitral velocities secondary to valvular obstruction and lower myocardial velocities in the setting of reduced output result in abnormally high E/e’ values that may not faithfully represent invasive filling pressures.41 LA volumes are often increased as an adaptation response to elevated pressures secondary to valvular obstruction. This is further compounded by the frequent occurrence of AF, which further distorts LA geometry. In keeping with these observations, current guidelines have suggested that recommended echocardiographic measures to identify LV diastolic function may not be accurate to assess LV filling pressures in the setting of significant mitral valve disease.40