Measurement and analysis of vibration in the myocardium telescopic motion for novel echo-graphic diagnosis

Abstract

We have already developed a novel ultrasonic-based method, namely, the phased tracking method, to measure the rapid velocity in the heart wall by accurately tracking the movement in the heart wall. By applying this method to in vivo experiments, the velocity signal of the heart wall with small amplitude, less than several micrometers on the large motion resulting from a heartbeat, can be successfully detected. There are high frequency components of up to several hundreds Hertz, which have not been previously investigated at all. In this study, after the papillary muscle had been extracted from an isolated rat heart, it was electrically stimulated, and the resultant muscular vibration was directly measured in the frequency range up to 2 kHz using a laser Doppler velocimeter in order to confirm if the high frequency vibrations occur during contraction and relaxation. For the injured myocardium, the power increase in the high frequency components becomes smaller. The experimental results support the hypothesis that the high frequency components are included in the velocity signal measured for the first time in the human interventricular septum by the phase tracking method using ultrasound.