成人心脏扭转运动生物力学机制的超声速度矢量成像研究

目的 应用超声速度矢量成像(velocity vector imaging,VVi)技术评价健康成人左室壁的旋转和扭转运动特征并探讨其成因.方法 应用VVI技术评价70例健康成人左室壁3个标准短轴水平和18个不同心肌节段的心内、外膜下心肌旋转特征和左室壁扭转运动特征,分别比较左室壁不同部位心肌在一个完整心动周期内的最大旋转角(Rmax)和左室壁心、内外膜下心肌的最大扭转角(Tmax)差异,并将左室壁的Tmax与左室壁不同短轴水平的Rmax做相关分析.结果 ①左室壁前间隔或前壁的Rmax比同一短轴水平其他心肌节段小(P>0.05).②一个完整心动周期内,左室壁基底水平与心尖水平旋转的主方向相反;左室壁乳头肌水平的Rmax小于基底水平或心尖水平(P<0.05),而左室壁基底水平与心尖水平的Rmax差异无统计学意义(P>0.05);左室壁的Tmax分别与左心室壁基底水平或心尖水平的Rmax呈线性正相关(P<0.01),而与乳头肌水平的Rmax零相关.③左室壁心内膜下心肌的Rmax大于心外膜下心肌(P<0.01);左室壁心内膜下心肌的Tmax大于心外膜下心肌[(11.44±4.82)°对(7.05±3.90)°,P<0.01].结论 健康成人左室壁扭转运动具有薄壁圆筒扭转特征,以生物力学理论为依据有望阐明心脏扭转运动生物力学机制.

Research on biomechanical mechanism of left ventricular rotation and twist in adults using ultrasonic velocity vector imaging

Objective To evaluate the characteristic of left ventricular rotation and twist in healthy adults using ultrasonic velocity vector imaging(VVI),and to discuss its biomechanical mechanism. Methods In 70 healthy adults, the rotational characteristic of left ventricular subendocardium and subepicardium at 3 differently standard shot-axis levels and 18 differently myocardial segments, and the torsional characteristic of left ventricular wall were evaluated via ultrasonic VVI. The maximum rotation angle(Rmax)at different sites of left ventricular wall and the maximum twist angle(Tmax)between left ventricular subendocardium and subepicardium in a completely cardiac cycle were compared respectively. Correlation tests were performed between left ventricular Tmax and the Rmax at different short-axis levels of left ventricular wall.Results ①To be compared with other myocardial segments, Rmax was smallest at antero-septal or anterior wall of the same left ventricular short-axis level(P>0.05).②The mainly rotational directions of the basal leveI and the apical level of left ventricular wall in a completely cardiac cycle were adverse.To be compared with basal or apical level of left ventricular wall,Rmax was smallest at papillary muscle level(P<0.05).and there was no statistical significance in Rmax between basal and apical level.There was positive colinearity between left ventricular Tmax and the Rmax of basal or apical level (P<0.01),but zero correlation was found between the Tmax and the Rmax of papillary muscle level.③Rmax of left ventricular subendocardium was bigger than that of subepicardium(P<0.01).Tmax of left ventricular subendocardium was bigger than that of subepicardium[(11.44±4.82)°vs(7.05±3.90)±,P<0.01].Conclusions Twist of left ventricular wall in healthy adults appeared the torsional characteristic of thin-wall cylinder.Elucidation of the biomechanical mechanism of cardiac twist is promising if basing on the principle of biomechanics.