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

Objectives: To 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.

Animals: 80 healthy adult dogs.

Methods: Dogs 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.

Results: All 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 (r(2) = 0.75); S' - moderate positive correlation (r(2) = 0.31); strain rate - moderate negative correlation (r(2) = 0.44); FAC and strain - weak negative correlations (r(2) = 0.22 and 0.14, respectively). Strain rate and FAC were positively correlated with heart rate (r(2) = 0.35 and 0.31, respectively). Allometric scaling generated bodyweight-based reference intervals for these RV systolic function indices.

Conclusions: Echocardiographic 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.