ECHOCARDIOGRAPHIC AND RIGHT-SIDED CARDIAC PRESSURE COMPARISON OF THE MULE AND HORSE

There are few physiologic studies that substantiate the popular belief that mules are superior to horses as working animals. The purpose of this study was to compare selected cardiac dimensions and right-sided cardiac pressures of mules and horses. Using 2-D real time and M-mode echocardiography and transjugular cardiac catheterization, resting car diac dimensions and right-sided pressures were recorded from 10 adult mules and 10 adult horses. The mules and horses were similar in size a nd physical condition, and both groups had served equally as pack anim als. The end diastolic left ventricular lumen diameter, interventricul ar septal thickness, left ventricular free wall thickness, and aortic root diameter measured (mean +/- SD) 9.51 +/- 0.92 cm, 2.63 +/- 0.34 c m, 2.28 +/- 0.31 cm, 7.9 +/- 0.57 cm, respectively, in mules, and 9.83 +/- 0.87 cm, 2.83 +/- 0.29 cm, 2.39 +/- 0.33 cm, 7.9 +/- 0.36 cm, res pectively, in horses. The end systolic left ventricular lumen diameter measured 5.79 +/- 0.96 cm in mules and 5.94 +/- 0.99 cm in horses, yi elding left ventricular luminal shortening fractions of 39.2 +/- 7.15% in mules and 39.7 +/- 6.91% in horses. Right atrial mean pressure was 5.3 +/- 2.3 mm of Hg in mules and 5.8 +/- 1.2 mm Hg in horses. Right ventricular peak systolic pressure was 47.9 +/- 4.9 mm Hg in mules and 47.7 +/- 3.5 mm Hg in horses. Pulmonary artery mean pressure was 27.3 +/- 3.2 mm Hg in mules and 28.1 +/- 3.6 mm Hg in horses. No significa nt differences were detected between mules and horses for the resting cardiac dimensions examined or right-sided pressures measured.