*Rosângela de Oliveira Alves, Roberto Baracat de Araújo, Euler Fraga Silva, Aparecido Antonio Camacho, Marlos Gonçalves Sousa
Echocardiography is an appropriate method for non-invasive serial evaluations of changes of the growing cardiac chamber dimensions of puppies. Since newborn dogs show differences from adult dogs in many morpho-functional aspects, and considering that they have a growing cardiac chamber and walls, this research was conceived to try to establish the profile of the regular echocardiographic evaluation during the neonatal period (from birth to thirty days), using both two-dimensional and M-mode, as well as Doppler (pulsed-wave and color flow), in order to make easier the interpretation of echocardiograms of immature dogs suspected of both congenital or acquired cardiac diseases.
Five litters of crossbreed dogs (31 puppies) were used. All animals were clinically healthy. One male and a female were chosen randomized from each litter to set up the model of physiologic cardiac development between the first and 30th day after birth. All 10 puppies that composed this group were submitted to echocardiographic evaluation each other day. Using the two-dimensional mode it was localized and identified the cardiac structures to allow mensuration, which was undergone through M-mode and Doppler, which allowed to verify the diameter of the aortic root, left and right ventricles internal diameters, thickness of both interventricular septum and left ventricle free wall. Moreover, a color flow and pulsed wave Doppler was performed, which allowed to evaluate the direction and velocity of the mitral, tricuspid, aortic and pulmonic flows.
It was possible to obtain satisfactory images of both M-mode and Doppler during the echocardiographic exam of this group of newborn dogs. The repeatability of the exam allowed to verify mild changes during the cardiac development. It was seen a positive linear correlation between the cardiac linear measures (M-mode), age and weight in both gender, despite weight seems to exert a higher effect over these variables than age.
The right ventricle showed a mild growth during the neonatal period, since it had bigger than left during birth, had the same size at 12 days after birth, and became smaller after the 22nd. day after birth. At the other hand, the left ventricle got almost three times its internal diameter during neonatal period. The flow across both mitral and tricuspid valves were positive and laminar, despite the A wave was bigger than the E wave during the evaluation period, differing from adult dogs. Both aortic and pulmonic flows were negative and its velocities increased in a significant way during the observed period.
This study allowed the conclusion that linear measurements of the heart, as well as the velocities of blood flows, are correlated to the body weight. These data are important to allow a satisfactory evaluation of the echocardiogram of puppies.
There were not significant differences in cardiac development between males and females during the newborn period.
The profile of mitral and tricuspid flows allowed suggest that in newborn dogs the atrial contraction has bigger importance in ventricular filling than the complacency of myocardium.
Echocardiography allowed a better understanding of dynamic anatomy of the newborn dog, which was previously studied in others experiments only through necropsies.