REPRODUCIBILITY AND REPEATABILITY OF M-MODE ECHOCARDIOGRAPHIC COLLECTED FROM 25 NORMAL HORSES

SUMMARY Three different operators with varying levels of experience made repeated echocardiographic measurements of the aortic root diameter, interventricular septal thickness, left ventficular internal diameter, and left ventricular free wall thickness of 25 horses using a 3.5 MHz transducer. Each operator followed specific guidelines in order to determine the reproducibility (inter-operator variation) and repeatability (intra-operator variation) of their measurements. Variations due to horse differences, operator differences, and horse by operator interactions were determined. The largest variation was due to differences between horses. Inter-operator-based variability was only significant with respect to interventricular septal and aortic root measurements. All other measurements were reproducible and repeatable when obtained by well-trained operators. The experience of operators affects reproducibility and repeatability, however. It was concluded that different operators could apply equine M-mode echocardiography to obtain measurements of ventricular chamber and free wall dimensions that can be legitimately