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