Two-dimensional transthoracic echocardiogram (2D TTE) from the apical 4 chamber view showing right atrial (RA) linear dimensions and area

Right atrial (RA) area (shown in yellow) is measured by planimetry of the atrial cavity in the apical four chamber view at end-systole (when the atrial cavity is at its largest). RA linear dimensions can also be measured in the apical four chamber view at end-systole. The normal reference limits for RA major-axis dimension (superior-inferior, from the center of the tricuspid annular plane to the uppermost aspect of the RA wall, shown as line 1) and minor-axis dimension (left-right, from the interatrial septum to the rightmost aspect of the RA wall, shown as line 2) are ≤5.3 cm and ≤4.4 cm, respectively.