In vivo analysis of adult zebrafish cardiac functions by Doppler-gated ultrahigh frame rate 80 MHz high frequency retrospective ultrasound imaging

The zebrafish has become a preferred animal model for studying cardiovascular developments. Recently, the high frequency ultrasound B-mode imaging has been utilized successfully to observe the heart of adult zebrafish. However, an ultrahigh frame rate echocardiography is needed in order to observe the detailed transient motions of zebrafish ventricle. In this study, the retrospective Doppler-gated technology was developed for this purpose. The frame rates of reconstructive B-mode and color flow images can respectively up to 40000 and 400 fps. Since the echocardiography exhibits high spatial and temporal resolutions, the transient motions of endocardium can be monitored for analyzing the ventricular functions of zebrafish. The timing of end diastole (E_D) and end systole (E_S) for ventricle were found by measuring the ventricular blood flow. Two ventricular function parameters, fractional shortening (FS) and fractional area change (FAC), were measured for evaluating the ventricular functions by using E_D and E_S with its corresponding ventricular dimension, respectively. The results indicated that the measured FSs were approximately 17% and 35% for long axis (LAx) and short axis (SAx), respectively, and the FAC was approximately 47%. All the results showed that retrospective high frequency echocardiography is an useful tool for studying the cardiac functions of normal adult zebrafish.