Assessment of left atrial volume in dogs: comparisons of two-dimensional and real-time three-dimensional echocardiography with ECG-gated multidetector computed tomography angiography.

Introduction: We hypothesized that real-time three-dimensional echocardiography (RT-3DE) was superior to two-dimensional echocardiography for the estimation of left atrial volume (LAV), using electrocardiographic (ECG)-gated multidetector computed tomography angiography (MDCTA) as a volumetric gold standard. The aim was to compare maximum LAV (LAV) and minimum LAV (LAV) measured by biplane area-length method (ALM), biplane method of disk (MOD) and RT-3DE with 64-slice ECG-gated MDCTA in dogs ANIMALS: The study included twenty dogs, anaesthetized for various diagnostic purposes and without evidence of cardiovascular disease.

Methods: Left atrial volume was estimated by ALM, MOD and RT-3DE following ECG-gated MDCTA. The results were compared with LAV from MDCTA and correlations were performed. The limits of agreement (LoA) between methods were evaluated using Bland-Altman analysis and intraclass correlations. Coefficients of variation were calculated.

Results: Area-length method (r = 0.79 and 0.72), MOD (r = 0.81 and 0.70) and RT-3DE (r = 0.94 and 0.82) correlated with MDCTA for LAV and LAV, respectively (all p < 0.05). Biases for LAV (-0.96 mL, 95% LoA: -5.6 to 3.7) and LAV (-0.67 mL, 95% LoA: -5.4 - 4.1) were minimal with RT-3DE, reflecting a slight underestimation. Conversely, MOD (LAVbias = 3.19 mL, 95% LoA: -5.7 - 12.1; LAVbias = 1.96 mL, 95% LoA: -4.6 - 8.5) and ALM (LAVbias = 4.05, 95% LoA: -5.7 - 13.8; LAVbias = 2.80 mL, 95% LoA: -3.9 - 9.5) suggested LAV overestimation. Intraobserver and interobserver variability were adequate.

Conclusions: Real-time three-dimensional echocardiography is a non-invasive, accurate and feasible method with superior accuracy to two-dimensional methods.