Abstract
BACKGROUND: Broadly applicable reference intervals (RIs) for measurements of left atrial (LA) and left ventricular (LV) size and function generated prospectively using statistically appropriate methods are limited. OBJECTIVES: To generate body size-independent RIs for linear, area, and volume measurements of LA size and LV size and function. ANIMALS: Healthy adult dogs (n = 122) of variable size and somatotype. METHODS: Prospective study. All dogs underwent an echocardiogram performed by the same examiner. Effects of body weight, sex, age, and heart rate were evaluated by regression and correlation analyses. Scaling exponents and prediction intervals were generated for linear measurements using the allometric equation. After normalization to body weight, 95% RIs were determined using nonparametric methods with 2.5 and 97.5 percentiles serving as the lower and upper limits (each with 90% confidence intervals), respectively. RESULTS: Linear LA and LV measurements were strongly correlated (R(2) ≥ 0.79) with body weight. Scaling exponents were close to the expected 1/3 (0.299-0.392). Prediction intervals for linear measurements of LV chamber size were considerably narrower than previously reported. Weak correlations (r = -0.42 to -0.50) among LV fractional shortening, fractional area change, and ejection fraction and body weight were identified. No other meaningful relationships were identified between the measurements and sex, age, and heart rate. CONCLUSIONS AND CLINICAL IMPORTANCE: Body size-independent RIs for several linear, area, and volume measurements of LA and LV size and function were generated prospectively from a large and diverse reference population and are available for clinical use.