Two-dimensional left atrium–to–aorta ratios and left ventricular M-mode transthoracic echocardiographic measurements in clinically normal adult Dachshunds

OBJECTIVE: To estimate the left atrium-to-aorta ratio (LA:Ao) and establish 95% prediction intervals for left ventricular M-mode transthoracic echocardiographic measurements in clinically normal adult Dachshunds. ANIMALS: 40 healthy Dachshunds. PROCEDURES: For each dog, 3 standard 2-D echocardiographic methods (diameter, circumference, and cross-sectional area) were used to measure the left atrium and aorta and calculate the LA:Ao from right parasternal short axis (RPSA) images obtained at the level of the aortic valve cusps. Left ventricular M-mode measurements were acquired from RPSA images obtained at the chordal level immediately below the mitral valve. Descriptive data were generated, and the 95% prediction intervals were calculated by use of an allometric scaling equation and linear regression and compared with those calculated on the basis of data obtained from dogs of multiple breeds in a previous study. RESULTS: The mean (SD) LA:Ao was 1.40 (0.13), 2.09 (0.17), and 2.85 (0.48) for the diameter, circumference, and cross-sectional area methods, respectively. The 95% prediction intervals for the left ventricular M-mode measurements determined by an allometric scaling equation on the basis of Dachshund-specific data were narrower than those determined on the basis of data obtained from dogs of multiple breeds. For that allometric equation, scaling exponents on the basis of Dachshund-specific data ranged from 0.129 to 0.397 and did not absolutely conform to the presumed index for linear measurements (ie, body weight(0.333)). CONCLUSIONS AND CLINICAL RELEVANCE: The LA:Aos and 95% prediction intervals calculated in this study can be used as preliminary guidelines for echocardiographic measurements of clinically normal Dachshunds.