Echocardiography is an noninvasive technique that utilizes high frequency ultrasound to evaluate structural, functional, and hemodynamic status of the cardiovascular system. With all the inherent potentials of this technique, its application has not been explored on lower vertebrates. The objective of our work was to apply ultrasonography technique, with an available commercial equipment (Echo camera--Aloka SSD 830 and Toshiba using probes of 5 and 7.5 MHz frequency emission) and to identify and characterize cardiac structures and blood flow in lower vertebrates. Specimens studied were Lophius piscatorius, Halobatrachus didactylus, and Bufo bufo. The probe was applied on the ventral middle line over heart chambers. Two-dimensional images were obtained from long and short axis incidences at various levels of cardiac chambers. During each cardiac cycle and for every specimen it was possible to identify the relation between each structure, to measure longitudinal and transversal diameters, to identify blood fluxes, and measure their velocities. The work we describe and discuss in our preliminary experience and data concerning the ultrasound study of some lower vertebrates. The cardiovascular apparatus of the different species we studied was a dynamic, phasic, and efficient contraction and relaxation mechanism. The phenomena could be well documented with two-dimensional echocardiography. The effect of the coupling phenomena of contraction and relaxation was also studied through the application of pulsed and color Doppler ultrasound. Two-dimensional and Doppler echocardiography can be easily applied to the study of the anatomy, morphology, and physiology of lower vertebrates. Well defined structures and cardiac chambers were displayed with this noninvasive imaging technique. Echo-Doppler ultrasonography is a reliable technique in these lower vertebrate specimens, to study cardiac structure and kinetics, and to identify and measure blood flow velocity. It can be used as an experimental model for cardiac function.

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