• horse;
  • echocardiology;
  • cardiac dimensions;
  • cardiac pressures;
  • mules


Although there are references to mules having an innate ability to withstand higher work loads than horses, there are relatively few physiological studies that substantiate these statements. The purpose of this study was to establish baseline information on cardiac dimensions and right sided pressures of the normal mule using echocardiography and cardiac catheterisation. Selected cardiac dimensions of 10 adult non-sedated mules were measured with 2-D real time and M-mode echocardiography. This was followed by catheterisation of the pulmonary artery, right ventricle and right atrium for measurement of pressures. End-diastolic left ventricular lumen diameter, interventricular septum thickness, left ventricular free wall thickness and aortic root diameter measured mean ± s.d. 11.1 ± 1.5 cm, 2.8 ± 0.3 cm, 3.3 ± 0.3 cm and 7.0 ± 0.9 cm, respectively and the end-systolic diameter for the left ventricular lumen measured 6.7 ± 1.3 cm yielding a fractional shortening of mean ± s.d. 40.4 ± 5.7%. Right atrial mean pressure, right ventricular peak systolic pressure and pulmonary arterial mean ± s.d. pressure measured 6.28 ± 1.6 mmHg, 55.3 ± 7.3 mmHg and 31.4 ± 5.4 mmHg, respectively. Although data collected from this study were limited to 10 normal animals, no significant difference in cardiac dimensions or right sided pressures were found compared to reported values in horses of similar size.