犬心尖在左室扭转中的作用及其机制的超声研究

目的 研究犬心尖在左室扭转中的作用及其机制.方法 14只实验犬麻醉状态下,用电加热器对其心尖进行加热,使加热区心肌完全坏死.用组织多普勒测量加热前、后左室扭转的角度,并在心尖心肌坏死区检测心尖旋转的角度.用应变率评价左室心肌收缩功能.通过比较加热前、后的左室扭转变化来评价心尖在左室扭转中的作用,并根据心尖旋转减低的百分比分析心尖旋转主要是主动旋转还是被动旋转.结果 心尖加热后,左室扭转由13.8°±2.3°减低为7.2°±3.3°(P<0.001),是由于心尖旋转减低所致(由12.4°±2.9°减低为4.9°±3.2°,P<0.001);心尖加热后,加热区收缩期应变率由(-1.83±0.72)s~(-1)减低为(-0.78±0.46)s~(-1)(P<0.001).结论 心尖在左室扭转中起重要作用;心尖旋转包括主动旋转和被动旋转,主动旋转为心尖旋转的主要组成部分;心尖主动旋转的力源于心尖本身的收缩,心尖被动旋转为心尖上部心肌驱使心尖发生的旋转.

The Role of Canine Apex in Left Ventricular Torsion and its Mechanism with Echocardiography

Objective The aim of our study is to try to evaluate the role of apex in left ventricular torsion through the damaged myocardium by apical heating.Methods The experiment was performed on 14 anesthetized dogs.All the apexes were heated with an iron and the heated zones became necrotic thoroughly and lost contraction.LV torsion was quantified with Doppler tissue imaging before and after apical heating.Apical rotation was measured at the transmural necrotic apex.Strain rate was used to evaluate left ventricular myocardial contractility.Role of apex in left ventricular torsion would be evaluated by comparing left ventricular torsion before and after apical heating.Results After apical heating,LV torsion decreased (7.2°±3.3° VS 13.8°±2.3°,P<0.001) due to the decrease of apical rotation (4.9°±3.2° VS 12.4°±2.9°,P<0.001).After apical heating,systolic strain rate of heated zone decreased (-0.78 s~(-1) 0.46 s~(-1) VS -1.83 s~(-1) ±0.72 s~(-1),P<0.001).Conclusions Apex plays a key role in LV torsion.Apical rotation includes active and passive apical rotations.Active apical rotation is the main part of apical rotation.The force of active apical rotation derives from apical contraction.Passive apical rotation is the rotation driven by LV upper myocardium.