Tissue Doppler Imaging : Assessment Of Myocardial Relaxation

Assessment Of Myocardial Relaxation

Early diastolic velocity (Ea or E’) of the miral annulus measured with TDI is a good indicator of LV myocardial relaxation. This is one of the most important components of myocardial diastolic function, the others being LV compliances and filling pressure. Longitudinal motion of the mitral annulus can be appreciated visually from the the parasternal long axis and apical four chamber views, but TDI records and demonstrates the velocity of the longitudinal motion in numerical value. In the normal heart with normal myocardial relaxation, E’ increases with an increasing transmitral gradient, increasing preload, exercise and dobutamine infusion. However when myocardial relaxation is impaired because of aging or a disease process, E’ is affected less or even unchanged by preload or transmitral gradient.

Velocities of longitudinal mitral anulus motion are best obtained from apical views. Although various locations of the mitral anulus can be interrogated with TDI, the two most frequently used locations are the septal and lateral mitral anulus. Usually, E’ from the lateral is higher (normal>15cm/s) than that from the medial anulus (normal>10cm/s). Regional myocardial dysfunction or valvular surgery involving the mitral annulus may effect mitral annulus velocities. A localized disease process, such as lateral myocardial infarction, can result in mitral annulus velocities being lower at the lateral annulus than at the septal annulus. Late diastolic velocity (Aa or A’) of the mitral annulus at the time of atrial contraction increases during early diastolic dysfunction, as is the case for the mitral inflow A wave, but decreases as atrial function deteriorates. A’ has been correlated with left atrial (LA) function.