Reproducibility and repeatability of M-mode echocardiographic measurementscollected from 25 normal horses

Three different operators with varying levels of experience made repeated e chocardiographic measurements of the aortic root diameter, interventricular septal thickness, left ventricular 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 (in ter-operator variation) and repeatability (intra-operator variation) of the ir 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 m easurements. All other measurements were reproducible and repeatable when o btained by well-trained operators. The experience of operators affects repr oducibility and repeatability, however. It was concluded that different ope rators could apply equine M-mode echocardiography to obtain measurements of ventricular chamber and free wall dimensions that can be legitimately comp ared to measurements obtained by others if operators are adequately trained and landmarks are clearly standardized.