Right Atrial Indexed Volume in Healthy Adult Population: Reference Values for Two-Dimensional and Three-Dimensional Echocardiographic Measurements.

Background: Current guidelines do not recommend routine assessment of right atrial volume due to the lack of standardized data. Three-dimensional wall-motion tracking (3D-WMT) is a new technology that allows us to calculate volumes without any geometric assumptions. The aim of this study was to define the indexed reference values for two-dimensional echocardiography (2D-echo) and 3D-WMT in adult healthy population and to assess the intermethod, intra-and interobserver agreement. Methods: Prospective study. Nonselected healthy subjects were enrolled. Every patient underwent a 2D-echo and a 3D-WMT examination. 2D-echo right atrial volume was obtained by using the area-length method (A-L) from four-and two-chamber view. 3D-echo volumes were assessed by 3D-WMT. Values were indexed by the patient's body surface area. Results: Sixty consecutive healthy subjects were enrolled. Mean age was 57 +/- 12-years old and 27 patients (45%) were male. Average indexed right atrial volume obtained by 2D-echo and 3D-echo was 16.76 +/- 8.15 mL/m(2) and 19.05 +/- 6.87 mL/m(2), respectively. Univariate linear regression analysis between 2D-echo and 3D-echo right atrial volumes shows a weak correlation between right atrial volume obtained with 2D-echo compared with 3D-WMT (r = 0.29, CI 95% 0.029-0.66, P = 0.033). The agreement analysis shows a similar result (intraclass correlation coefficient [ICC] = 0.28). The intra-and interobserver agreement analysis showed a better agreement when using 3D-WMT. Conclusions: This is the first study that reports the reference indexed right atrial volume values by means of 2D-echo and 3D-echo in healthy population. 3D-WMT is a feasible and reproducible method to determine right atrial volume.