Echocardiographic reference intervals for right ventricular indices, including 3‐dimensional volume and 2‐dimensional strain measurements in healthy dogs

Abstract Background There is currently a lack of reference intervals (RIs) for the novel measures like 3‐dimensional (3D) echocardiography or speckle‐tracking strain for assessment of right ventricular (RV) structure and function. Objectives To generate RIs and to determine the influence of age, heart rate, and body weight (BW) on various RV function indices using a dedicated RV software for 3D RV end‐diastolic volume (EDV), end‐systolic volume (ESV), ejection fraction (EF), global and free wall RV longitudinal strain (RVLS), end‐diastolic area (RVEDA), end‐systolic area (RVESA), fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tissue Doppler imaging (TVI)‐derived systolic myocardial velocity of the lateral tricuspid annulus (S′). Animals Healthy adult client‐owned dogs (n = 211) of various breeds and ages. Methods Prospective study. Reference intervals were estimated as statistical prediction intervals using allometric scaling for BW‐dependent variables. Right‐sided (upper limit) or left‐sided (lower limit) 95% RIs were calculated for every variable. Inter‐ and intraobserver variability was determined. Results Most variables showed clinically acceptable repeatability with coefficient of variation less than 10. Upper or respectively lower RI after allometric scaling to normalize for different BWs were: EDVn ≤ 2.5 mL/kg0.942, ESVn ≤ 1.2 mL/kg0.962, TAPSEn ≥ 4.5 mm0.285, RVEDAn ≤ 1.4 cm2/kg0.665, RVESAn ≤ 0.8 cm2/kg0.695, and TVI S′n ≥ 5.6 cm/s/kg0.186. The calculated limits for indices without allometric normalization were: EF > 42.1%, FAC > 30.0%, free wall RVLS < −20.8%, and global RVLS < −18.3%. Conclusions Echocardiographic RIs for RV structure and function are provided.