[Effects of age on left ventricular twist-displacement loop assessed by velocity vector imaging]

To assess effect of age on the characteristic of left ventricular (LV) twist-displacement loop in health volunteers by velocity vector imaging (VVI) and to provide a new method for LV function evaluation in clinic.

After obtaining basal and apical LV short-axis images in 98 healthy volunteers (18-75 years old) by 2-dimensional echocardiography, we use VVI software to analysis LV twist motion and radial displacement at each plane off-line. The peak LV twist (Ptw), the peak untwist velocity (PutwV), the proportion of untwist in isovolumetric relaxation period (Iutw%) and LV radial displacement (Dis) were measured and calculated. Then we constructed LV twist-displacement loop and compared the characteristic of them among different groups.

Ptw increased gradually with the increase in age. The biggest PutwV was in the group of 30-60 years old. Iutw% increased gradually before 60 years old, then decreased after that. Dis was not obviously different among the three groups. The characteristic of LV twist-displacement loop was like the configuration of 8. There was a linear relation between twist and displacement during systole, and the slope increased gradually with the increase in age. During early diastole, the relatively small radial expanding displacement displayed with untwisting, resulting in a much steeper twist-displacement relationship curve occurred in each group, which was getting smooth gradually when the radial expanding displacement increased during mid to late diastole.

VVI can be used to effectively and noninvasively assess LV twist-displacement loop with change in age and provide important information for LV function. The effect of age must take into account when evaluate the LV function by the twist-displacement loop.