Ultrasonic visualization of propagation of myocardial vibration driven by electrical excitation of myocardium of rat in ex vivo experiment

Abstract

For the realization of noninvasive and regional myocardial tissue characterization, in the present study, we attempted to elucidate the characteristics of the myocardial response to electrical excitation and its propagation by an ex vivo experiment using a rat left ventricular wall. To visualize such a propagation phenomenon, whose speed is up to several m/s, high-frame-rate ultrasound was used to measure the myocardial vibrations driven by electrical excitation at 72 points along the heart wall with 200 µm intervals at a frame rate of 3472 Hz. The propagation of myocardial vibration was visualized by estimating the delay time between vibration waveforms measured in the reference ultrasonic beam and each ultrasonic beam using the cross-correlation function between the vibration waveforms. From the estimated delay time, we visualized the propagation of myocardial vibration caused by electrical excitation. The propagation speed was estimated to be 2.5 m/s in the entire excised myocardium. It was also estimated to be 1.8 m/s in the middle of the heart wall and 2.2 m/s at the internal and external surfaces of the leftventricular wall. The results showed that the myocardial vibration driven by electrical excitation could be measured with high-frame-rate ultrasound.

Introduction of measurement techniques in ultrasonic electronics: Basic principles and recent trends

“…[394][395][396][397] The measurement of tissue structure and function, such as viscoelasticity and roughness, to assess the quality of tissue was also achieved by measuring basic quantities, such as velocity, displacement, and thickness using ultrasound. The development of image processing techniques, including signal gathering, image forming, and picture processing, 359,363,381,[427][428][429][430][431][432][433][434][435][436][437][438][439][440] as well as the use of the acoustic radiation force 336,423,441,442) and actuation techniques 443) for remote assessment have also been researched.…”

Accurate evaluation of viscoelasticity of radial artery wall during flow-mediated dilation in ultrasound measurement

“…1, the arterial blood pressure waveforms p A (t) and p B (t) at two points on the left radial artery were simultaneously measured using two pressure sensors. The time delay τ from p A (t) to p B (t) was determined by maximizing the crosscorrelation function 23) as…”

Analysis of arterial wall motion for measurement of regional pulse wave velocity

“…Various studies have been conducted recently for the improvement of the temporal resolution in ultrasonic imaging techniques, e.g., methods of decreasing the density of scan lines, 21) the electrocardiogram (ECG) gating technique, 22) and ultrafast ultrasound imaging using unfocused transmit beams. [23][24][25][26][27][28][29][30][31][32] In particular, ultrafast ultrasound imaging realizes an imaging frame rate of more than 1000 frames per second (fps) and is used for measurements of cardiovascular dynamics [33][34][35][36] and blood flow. 30,[37][38][39][40][41] Ultrafast ultrasound imaging is a promising method for the measurement of the regional PWV, and some studies have been conducted for the measurement of the regional PWV by ultrafast ultrasound imaging.…”