Research on diastolic properties of the myocardium by imaging propagation of shear wave along heart wall

通过超声测量心肌运动，我们已经发现在收缩末期主动脉瓣关闭时，脉冲波是自发产生的。由于心肌粘弹性在评估心脏舒张特性中至关重要，因此本研究使该生理现象在体内无创测量如下：1使用稀疏扇形扫描，以足够高的帧率几乎同时测量沿心脏壁设置的数千个点的脉冲波。连续的空间相位分布清楚地显示了波沿心壁的传播。对每个频率分量确定波的相速度。通过与兰姆波沿浸入血液的粘弹性板传播的理论相速度色散进行比较，无创地确定了瞬时粘弹性在临床超声诊断系统中实现了测量原理通过在一个弹性球壳中施加一个小脉冲，我们证实了球壳的粘弹性可以测量，其误差小于力学试验测量的粘弹性的10%将该方法应用于5名健康受试者，证实了脉冲波在连续心动周期中的传播速度具有足够的再现性我们证实5名受试者的粘弹性值之间的差异小于20%，并且主动脉瓣关闭后的粘弹性瞬态相似。粘弹性估计值与文献中犬心脏壁的测量值相似通过对10例陈旧性心肌梗死患者应用该方法，我们发现各病变区域的振幅和传播速度都有所下降。这些结果与文献中利用纵波得到的结果一致综上所述，在此基础上，我们建立了一种在体内测量心肌粘弹性的方法。这些临床结果表明，该方法具有无创揭示心肌异质性的潜力。少

By ultrasonic measurement of the myocardial motion, we have already found that pulsive waves are spontaneously excited by aortic-valve closure at end-systole. Since myocardial viscoelasticity is essential in the evaluation of heart diastolic properties, this study makes the physiological phenomenon to be measured noninvasively measured in vivo as follows:1 Using a sparse sector scan, the pulsive waves were measured almost simultaneously at several thousand points set along the heart wall at a sufficiently high frame rate. The consecutive spatial phase distributions clearly revealed wave propagation along the heart wall. The phase velocity of the wave is determined for each frequency component. By comparing the dispersion of the phase velocity with the theoretical one of the Lamb wave, which propagates along the viscoelastic plate immersed in blood, the instantaneous viscoelasticity is determined noninvasively.2 We realized the principle of the measurement in a clinical ultrasonic diagn … More ostic system.3 By actuating a small pulse in an elastic spherical shell, which was made as a model of the heart, we confirmed that the viscoelasticity of the spherical shell can be measured with an error less than 10% of the viscoelasticity measured by the mechanical test.4 By applying the developed method to 5 healthy subjects, we confirmed the sufficient reproducibility of the propagation velocity of the pulsive wave among the consecutive cardiac cycles.5 We confirmed that the difference among the viscoelasticity values estimated from the 5 subjects is less than 20% and the transient of the viscoelasticity just after the aortic valve closure is similar. The viscoelasticity estimates are similar to those measured for the canine heart wall in literature.6 By applying the method to 10 patients with old myocardial infarction, we found that the amplitude and the propagation speed were decreased in each of the diseased areas. These results correspond to that obtained by using the longitudinal waves in literature.7 In conclusion, based on the new findings, we developed a means to measure the myocardial viscoelasticity in vivo. These clinical results indicate that the method has a potential for noninvasively revealing myocardial heterogeneity. Less