“…This compensatory phenomenon is lost in patients with diastolic dysfunction, resulting in reduced left ventricular (LV) filling and stroke volume (10)(11)(12)(13)(14)(15). Diastolic function is assessed by standard measures of ventricular relaxation or adenosine triphosphate-dependent part of ventricular diastole that include E wave, A wave, E/A ratio, E′, A′, and myocardial performance index or Tei index by Doppler echocardiography (16)(17)(18)(19). Of all these variables, early diastolic mitral annular velocity (E′), as measured by tissue Doppler imaging (TDI), reflects LV relaxation and is mostly independent of both preload and heart rate (18).…”