Influence of left ventricle longitudinal axis translation on rotation measurements in 3D echocardiography

In 3D echocardiography, the left ventricular (LV) longitudinal axis is often determined in end-diastole as a line perpendicular to the mid-point of the mitral valve plane pointing to the tip of the apex. It is assumed that the LV rotates around the longitudinal axis defined at end-diastole. However, it is a known fact that neither the mitral valve plane nor the apex are fixed during a cardiac cycle; accordingly, the longitudinal axis is dynamically moving in space rather than being motionless. Then, the following question arises: do we need not to consider the movement of the longitudinal axis for measurements, such as rotation and twist, with respect to the longitudinal axis? This study investigates how LV long-axis movement affects the rotation measurements and whether it is relevant in the analysis of 3D echocardiography data. To this end, two methods are examined. In Method 1, the configuration of the longitudinal axis is updated with the deformation of the LV, whereas in Method 2 the long axis configuration is fixed to its position at end-diastole during cardiac cycle. The comparison of two methods reveals a huge influence of the longitudinal axis translation on rotation measurements while the twist is not notably affected.