Abstract

During the past 10 years we have been studying the application of echocardiography to the non-invasive study of heart morphology and physiology of a marine teleost, the Lusitanian Toadfish (Halobatrachus didactylus), regarding its use as a reliable experimental model to study the cardiac contraction regulatory mechanisms, namely adaptation mechanisms to environmental, pharmacological and physiopathological changes. Echocardiographic examination was performed in vivo on anaesthetised individuals. Bidimensional images of heart structures were obtained by bidimensional echocardiography and M-mode. Doppler velocity spectrum of cardiac flows were also recorded (ventricular filling and ejection flows and coronary flow) by pulsed and colour-Doppler. Several indices of ventricle performance were determined based on the capacity of the blood to pump blood (stroke volume and cardiac output), the ability to generate force (pressure gradients), the ability to shorten with each contraction (ejection fraction and fractional shortening) and the temporal relationships of contraction and relaxation (systolic and diastolic intervals). These parameters allowed study of systolic and diastolic functions of the H. didactylus heart. Coronary reserve flow was also calculated, based on spectral Doppler records of coronary blood flow. This work proved that all these parameters can be obtained by a non-invasive approach in lower vertebrates and are useful to study the cardiac contraction regulation in these animals. The volumetric and heamodynamic variations of H. didactylus ventricle, were similar to other sedentary species, derived with other techniques.

The strongest advantage of echocardiography is its non invasive approach, which provides cardiac structural images with detailed morphological and functional information, from intact animals. The application of a non invasive technique guaranties the absence of injury to the patient, which allowed to repeat the examination throughout time, on the same animal. This work proves the utility of echocardiography to study ventricular functional indices on this specie and opens the chance to study other fish species and other vertebrate groups. Once defined the functional parameters in basal conditions, these cardiovascular parameters can be useful to evaluate physiopathological changes induced by environmental, handling or captivity stress.

Acknowledgements

This work was supported by: UIC and CCMar (pluriannual funding from FCT).