Cardiomyocytes are sustained and inserted into a connective tissue skeleton that has different distribution depending up on the properties of the region in which it stands. The purpose of this study was to quantify the proportion of connective tissue in relation to the arrangement of cardiomyocytes of left and right ventricles and interventricular septum in myocardium of six mixed breed, ill trifted adult horses, of both sexes, used for traction. With hearts still fresh and with the aid of a digital caliper, it was estimated the height of left ventricle, the heart's width, the heart's circumference and the thickness of the ventricular free walls and interventricular septum. The fragments on the middle third of the interventricular septum and free walls of the ventricles were subjected to conventional histological technique. The blocks were cut with thickness of 5µm and stained with Picrosirius Red, Gomori Trichrome and Azan Trichrome to show the connective tissue. The slides were analyzed using optical microscope coupled to a digital analysis program Image-Pro Plus®. The average proportion of connective tissue in the left ventricle was 6.1+3.7%, in the interventricular septum and it was observed a mean of 6.8+3.6%. In the right ventricle the average was 6.0+3.0%. Applying the H test of Kruskal-Wallis, it was found that there was statistical difference between the different dyes used for each region. In the Pearson correlation test it was not found pattern correlation between the thickness of the regions analyzed and the proportion of connective tissue
heart; morfometry; myocardium; cardiomyocytes