Abstract 19169: Best Method for Right Atrial Volume Assessment by Two-Dimensional Echocardiography: Validation With Magnetic Resonance Imaging

Abstract

Background: In contrast to left atrial volume, 2D echocardiographic methods for estimating right atrial (RA) volume have not been standardized and therefore not used in clinical assessment. Methods: RA volume was assessed in patients who underwent comprehensive 2D echocardiography and MRI assessment of the heart for clinically indicated reasons. The volumes obtained using three 2D echocardiography methods, and linear RA major and minor dimensions were compared correlated with RA volume determined by MRI. The 3 echocardiographic methods for assessing RA volume included: 1) biplane area length method using 4 chamber view twice (Biplane 4C-4C); 2) biplane area length method using 4 chamber and subcostal view (Biplane 4C-Subcostal); and 3) Single plane Simpson’s method of disc (Single plane 4C-Simpson’s). These echocardiographic methods were also evaluated for their accuracy in discriminating RA enlargement. Results: A total of 51 persons (33 female, 18 male), mean age 53 ± 14 years underwent cardiac MRI and echocardiography. All 3 echocardiography volumetric methods performed well with correlation being 0.98 for each. In terms of bias and limits of agreement, biplane 4C-4C (bias -4.81 mL, limits of agreement ± 9.8 mL) and single plane Simpson’s (bias -5.15 mL, limits of agreement ± 10.1 mL) outperformed biplane 4C-subcostal (bias -8.36 mL, limits of agreement ± 12.5 mL). Linear measurements performed poorly with low correlation (RA major, 0.49; RA minor 0.54), high degree of bias and wide limits of agreement. Using MRI as reference, the accuracy for discriminating large from non-large was high for all 3 methods (all >90% if a cut-off at 55 mL was used). In contrast, accuracy for RA major was at best only 80% and 62% respectively, cutting at 50 mm for major, and 36 mm for minor. The interobserver variability was satisfactory across all three volume methods (range 5.8- 7.3 mL). Conclusions: Using MRI as reference, biplane 4C-4C and single plane Simpson’s are highly accurate 2D echocardiography methods, superior to biplane 4C-Subcosta method for estimating RA volume. Linear methods are inaccurate and should be abandoned.