Echocardiographic assessment of right ventricular systolic function in conscious healthy dogs: Repeatability and reference intervals

ObjectivesTo determine the feasibility, repeatability, intra- and interobserver variability, and reference intervals for 5 echocardiographic indices of right ventricular (RV) systolic function: tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), pulsed wave tissue Doppler imaging-derived systolic myocardial velocity of the lateral tricuspid annulus (S'), and speckle-tracking echocardiography-derived global longitudinal RV free wall strain and strain rate. To explore statistical relationships between RV systolic function and age, gender, heart rate, and bodyweight.Animals80 healthy adult dogs.MethodsDogs underwent 2 echocardiographic examinations. Repeatability and intra-observer and inter-observer measurement variability were quantified by average coefficient of variation (CV). Relationships between RV function and age, heart rate and bodyweight were estimated by regression analysis.ResultsAll indices were acquired with clinically acceptable repeatability and intra- and inter-observer variability (CVs < 10%). No differences were identified between male and female dogs. Allometric scaling by bodyweight demonstrated significant, clinically relevant correlations between RV function and bodyweight (all p ≤ 0.001) as follows: TAPSE – strong positive correlation (r2 = 0.75); S’ – moderate positive correlation (r2 = 0.31); strain rate – moderate negative correlation (r2 = 0.44); FAC and strain – weak negative correlations (r2 = 0.22 and 0.14, respectively). Strain rate and FAC were positively correlated with heart rate (r2 = 0.35 and 0.31, respectively). Allometric scaling generated bodyweight-based reference intervals for these RV systolic function indices.ConclusionsEchocardiographic indices of RV systolic function are feasible to obtain, repeatable, and affected by bodyweight. Studies of these indices in dogs with cardiovascular disease are needed.