M-MODE ECHOCARDIOGRAPHY STUDY IN GROWING SPANISH MASTIFFS

The growth of the heart in proportion to bodyweight was studied by M-m ode echocardiography in 66 Spanish mastiffs aged from one to 12 months and from two to four years. Measurements of the right and left ventri cular cavities, septal and parietal wall thicknesses, aorta, left atri um, D-E excursion of the mitral valve and distance between the maximum aperture of the mi h al valve and the interventricular septum, were s hown to have a curvilinear increase closely related to the development of bodyweight. Least squares regression analysis of the logarithmical ly transformed data provided the power-law equations relating each ech ocardiographic measurement to bodyweight. The exponential powers of bo dyweight varied from 0.22 to 0.45. From the direct measurements the fo llowing cardiac indices were determined: ratio of right/left ventricul ar cavity, shortening fraction, percentage of septal and parietal wall thickness and ratio of aorta/left atrium. The highest coefficient of determination was for the right ventricular/left ventricular ratio.