A study of the adult zebrafish ventricular function by retrospective doppler-gated ultrahigh-frame-rate echocardiography

The zebrafish (Danio rerio) has become a preferred animal model for studying various human diseases, particularly those related to cardiovascular regeneration; therefore, a noninvasive imaging modality is needed for observing the cardiac function of zebrafish. Because of its high resolution, high-frequency ultrasound B-mode imaging has recently been used successfully to observe the heart of adult zebrafish. However, ultrahigh-frame-rate echocardiography combining Bmode imaging and color flow imaging is still needed to observe the detailed transient motions of the zebrafish ventricle. This study develops an 80-MHz ultrahigh-frame-rate echocardiography system for this purpose, based on retrospective Doppler- gated technology. B-mode and color flow images of the cardiovascular system of the zebrafish were reconstructed by two-dimensional autocorrelation at maximum frame rates of up to 40 000 and 400 fps, respectively. The timings of end diastole (ED) and end systole (ES) of ventricle can be determined by using this high-resolution image system. Two ventricular function parameters-fractional shortening (FS) and fractional area change (FAC)-were measured for evaluating the ventricular function by using EDand ESwith their corresponding ventricular dimensions. The experimental results indicated that the measured FS values were 42 ± 4% (mean ± standard deviation) and 60 ± 13% for the long axis and short axis of the ventricle, respectively, and that FAC was 77 ± 9%. This is the first report of these ventricular function parameters for a normal adult zebrafish. The results showed that retrospective high-frequency echocardiography is a useful tool for studying the cardiac function of normal adult zebrafish.