RESUMO
Objective To investigate the left ventricular (LV) torsion parameters of type B WolffParkinson-White syndrome (B-WPW) and to explore alternation of the left ventricular motion pattern in patients with B-WPW.Methods Thirty-eight patients with B-WPW were studied.And 40 volunteers were selected as control.Two-dimensional speckle tracking imaging (2D-STI) was used to acquire left ventricular torsion parameters,including peak value and time to peak value of LV twist,LV apex rotation,and LV base rotation.Apical-basal rotation delay (RDA-B) was calculated.Biplane Simpson method was used to measure LV end-diastolic volume (LVEDV),end-systolic volume (LVESV) and ejection fraction (LVEF).All above parameters were measured in patients with B-WPW before (B-WPW-B group) and after (B-WPW-A group) radiofrequency catheter ablation and in control group.The QRS width of lead Ⅱ was recorded,and the relationships between all above parameters with the RDA-B or QRS width were analyzed.Results Compared with the contrd group,in patients with B-WPW,the peak value of LV apex rotation (RotA),LV base rotation (RotB) and LV twist (TwistLV) were lower(LV base was more obvious than LV apex)(P ＜0.05),the time to RotB (TTPB) was shorter (P =0.004),RDAB was longer(P =0.002),the left ventricular enlarged and the QRS prolonged (P =0.000).After radiofrequency catheter ablation,the left ventricular torsion parameters in patients with B-WPW recovered significantly(P ＜0.05),but still lower than those in the control group(P ＜0.05).Conclusions The left ventricular motion pattern of patients with B-WPW alters,including the changes of peak value and time to peak value in LV apex rotation,LV base rotation and LV twist,as well as LV myocardium dyssynchrony.The motion pattern of LV in patients with B-WPW is improved in acute stage after radiofrequency catheter ablation but not yet recover totally.
RESUMO
The purpose of this study was to examine the effect of hopping tempo on the stretch reflex of the soleus muscle at the landing phase during continuous hopping. The M 1 and M 2 components of stretch reflex of the soleus muscle and angular velocity of the ankle joint were recorded at the landing phase during hopping under four hopping tempos with frequencies of 1.0, 1.5, 2.0, and 2.5 Hz. The electromyogram (EMG) activities in the soleus muscle during the landing and the jumping phases were separated under 1.0, 1.5 and 2.0 Hz conditions, but EMG's for both phases were overlapped under 2.5 Hz condition. Furthermore, at 1.0 and 1.5 Hz, a non-active EMG phase was observed between the landing and the jumping phases ; but this non-active phase disappeared at 2.0 Hz. The M 1 and M 2 components at 2.0 Hz showed significantly (p<0.01) larger values than those at 1.0 and 1.5 Hz. However, there was no significant difference observed between the components at 1.0 and 1.5 Hz. The M 2 component showed a significantly (p <0.01) smaller value than the M 1 component at 1.0 and 1.5 Hz ; but there was no significant difference at 2.0 Hz. The angular velocity of the ankle joint showed no significant difference under any of the conditions. These findings suggest that stretch reflex at landing during hopping may be inhibited at the motion pattern of the inactive phase between the landing and the jumping phases in EMG's. In addition, the stretch reflex is not only related to mechanical muscle stretching, but is also under the influence of the superior nerve center.