Common two-dimensional echocardiographic estimates of aortic linear dimensions are interchangeable Ranko Georgiev, DVM a , Mark Rishniw, BVSc, MS, PhD b,c, *, Ingrid Ljungvall, DVM, PhD d , Nuala Summerfield, BVMS e a Central Veterinary Clinic, Sofia, Bulgaria b Department of Clinical Sciences, Cornell University, Ithaca, NY 14853, USA c Veterinary Information Network, Davis, CA 95616, USA d Department of Clinical Sciences, Swedish University of Agricultural Science, Uppsala, Sweden e Geneva, Switzerland Received 4 April 2012; received in revised form 18 February 2013; accepted 24 February 2013 KEYWORDS Aorta; Echocardiography; Measurement; Dog; Cat Abstract Objective: To compare two echocardiographic methods of measuring aortic diameter in short-axis projections. Methods: Right-parasternal short-axis 2-dimensional projections of the left atrium and aorta were obtained from dogs and cats undergoing routine cardiac evaluation. Two investigators measured the aortic valve linear dimension using 2 methods: along the commissure between the non-coronary and right-coronary cusps and along the commissure between the non-coronary and left-coronary cusps. Inter- observer and intra-observer variability and agreement were assessed by comparing blinded measurements with each method by 4 trained observers on a standardized set of images. Measurements were compared for agreement using the limits of agreement analysis. Variability between observers was compared by examining residuals and intraclass correlation. Results: 274 canine and 100 feline aortic valve images were measured in the first part of the study. One observer demonstrated slight proportional bias, while the other observer showed more variability (less agreement). When results were pooled for both investigators, no bias was identified, and 95% limits of agreement were Æ10% of the mean measurement for both species. In the second part of the study, 106 images were measured. Intraobserver variability was <4% for all observers. Inter-observer agreement was very high. Individual bias was identified in some * Corresponding author. Department of Clinical Sciences, Cornell University, Ithaca, NY 14853, USA. E-mail addresses: mrishniw@vin.com, mr89@cornell.edu (M. Rishniw). 1760-2734/$ - see front matter ª 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jvc.2013.02.002 Journal of Veterinary Cardiology (2013) 15, 131e138 www.elsevier.com/locate/jvc