M‐mode echocardiography study in growing Spanish mastiffs

The growth of the heart in proportion to body‐weight was studied by M‐mode echocardiography in 66 Spanish mastiffs aged from one to 12 months and from two to four years. Measurements of the right and left ventricular cavities, septal and parietal wall thicknesses, aorta, left atrium, D‐E excursion of the mitral valve and distance between the maximum aperture of the mitral valve and the interventricular septum, were shown to have a curvilinear increase closely related to the development of bodyweight. Least squares regression analysis of the logarithmically transformed data provided the power‐law equations relating each echocardiographic measurement to bodyweight. The exponential powers of bodyweight varied from 0.22 to 0.45. From the direct measurements the following cardiac indices were determined: ratio of right/left ventricular 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.