Evaluation of left ventricular torsion by two dimensional tissue tracking system

背景：二维组织跟踪(2DTT)技术可以利用模式匹配的方法来跟踪局部心肌组织。2DTT可分别评价心内膜(Endo)和心外膜(Epi)的左心室扭转。我们的目的是用2DTT评价特发性扩张型心肌病左室扭转对小剂量多巴酚丁胺(道布)输注的反应。方法：对10例扩张型心肌病患者进行研究。采用配备2DTT软件的日立EUB-7500型超声仪，分别在静息状态和道布灌流(5，10μg/kg/min)过程中获得LV的基础和心尖短轴切面。在每个基础和根尖切面上，在Endo和Epi各等分放置8个点。在整个心脏周期中，系统会自动跟踪这些点的运动。通过定制软件确定每一帧的旋转中心，并计算每个点的旋转角度并取其平均值。LV扭转定义为基础旋转角与心尖旋转角的净差。采用双平面Simpson方程计算左心室舒张末容量和左心室收缩末期容量。结果：10例患者中有7例静脉滴注道布10μg/kg/min后ESV下降10%以上。在应答者中，输注道布10μg/kg/min时，根尖内旋转和根尖外旋均增加(内径：1.2±1.1至3.6±1.8°，外周角：0.8±0.7至2.3±1.2，p&lt；0.01)，但基础旋转角在整个研究过程中没有变化。因此，经道布输注后，左心室内膜和外壁的扭转增加(内腔：3.1±1.7°至5.7±1.6°，外壁：2.4±1.0至4.6±1.7，p&lt；0.0 5)。另一方面，对于左心室对道布输注反应差的患者，道布输注期间基础和心尖旋转角不变。结论：正性肌力刺激可使心肌旋转增强，尤其是心尖部，这可能反映了DCM的心肌收缩储备。

Background: The Two-Dimensional Tissue Tracking (2DTT) technique can trace regional myocardial tissue using pattern matching method. The 2DTT has a capability to clinically evaluate the left ventricular (LV) torsion in endocardium (Endo) and epicardium (Epi) separately. Our objective was to characterize the response of LV torsion to low-dose dobutamine (Dob)infusion using 2DTT in idiopathic dilated cardiomyopathy (DCM). Methods: Ten patients with DCM were studied. We acquired LV basal and apical short-axis views both at rest and during Dob infusion (5, 10μg/kg/min) using Hitachi EUB-7500 ultrasound machine equipped with 2DTT software. Eight points were manually placed both at Endo and Epi equally in each basal and apical view. The movements of these points were automatically tracked by the system throughout a cardiac cycle. The center of rotation in each frame was determined by customized software, and rotation angle of each point was calculated and averaged. The LV torsion was defined as net-difference between basal and apical rotation angle. LV end-diastolic volume and LV end-systolic volume (ESV)were assessed by the biplane Simpson's equation. Results: Seven of 10 patients showed more than 10% reduction in ESV after 10μg/kg/min Dob infusion(responder). In responders, both apical Endo and Epi rotation increased at 10μg/kg/min Dob infusion (Endo: 1.2±1.1 to 3.6±1.8°, Epi: 0.8±0.7 to 2.3±1.2, p<0.01, respectively), however, basal rotation angles unchanged throughout of study. Consequently, the LV torsion in Endo and Epi increased after Dob infusion (Endo: 3.1±1.7 to 5.7±1.6°, Epi: 2.4±1.0 to 4.6±1.7, p<0.05, respectively).On the other hand, in patients with poor LV response to Dob infusion, basal and apical rotation angles unchanged during Dob infusion. Conclusions: The augmentation of LV rotation was observed especially in apex by inotropic stimulation, which may reflect myocardial contractile reserve in DCM.