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

通过对心肌运动的超声测量，我们已经发现在收缩末期关闭主动脉瓣时会自发地产生脉冲波。由于心肌粘弹性在评价心脏舒张期特性中是必不可少的，本研究将这一生理现象无创性地在活体测量如下：1采用稀疏扇形扫描，以足够高的帧速率几乎同时测量沿心壁设置的几千个点的脉搏波。连续的空间相位分布清楚地显示了波在心壁上的传播。对于每个频率分量，确定波的相速度。通过比较相速度色散和兰姆波的理论色散，非侵入性地确定了瞬时粘弹性。2.在临床超声诊断…中实现了测量原理3通过在弹性球壳中激励一个小脉冲作为心脏的模型，我们证实了球壳的粘弹性可以被测量，其误差小于机械测试所测量的粘弹性的10%。4通过对5名健康受试者应用所开发的方法，我们证实了脉冲波在连续的心动周期中传播速度的足够的重复性。5我们证实了5名受试者的粘弹性估计值之间的差异小于20%，并且主动脉瓣关闭后的粘弹性的瞬变是相似的。粘弹性估计与文献中对犬心壁的测量结果相似。6通过对10例陈旧性心肌梗死患者应用该方法，我们发现每个病变区域的波幅和传播速度都有所降低。这些结果与文献中利用纵波获得的结果相吻合。7综上所述，基于新的发现，我们发展了一种测量在体心肌粘弹性的方法。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。较少

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