Background: Left atrial (LA) size provides important information about severity and prognosis in various cardiovascular diseases. Measurement of volume index in 4-chamber and 2-chamber views by 2-dimensional (2D) transthoracic echocardiography (TTE) is recommended for the assessment of LA size. As LA and left ventricle (LV) lie in different axes standard apical TTE views lead to foreshortening of the LA.

 

Aim: This study sought to evaluate measurements of LA volume index (LAVi) in standard as well as in dedicated atrial-focused 4-chamber and 2-chamber views by 2D TTE and to compare them with measurements by 3-dimensional (3D) TTE as the reference method.

 

Methods: 39 consecutive patients (61±17 years) who were assigned for LV function analysis were included. Standard 2D TTE study was performed with additional atrial-focused 4-chamber and 2-chamber views dedicated for LA quantification with image optimization to avoid LA foreshortening by maximizing LA length and area in each view. LAVi was measured by biplane method of discs in standard apical 4-chamber and 2-chamber views as well as in the dedicated atrial-focused 4-chamber and 2-chamber views. 3D TTE was performed for measurement of 3D LAVi. Furthermore, length of the LV was measured in standard 4-chamber and 2-chamber views as well as in the atrial-focused 4-chamber and 2-chamber views.

 

Results: LAVi by standard view analysis was smaller compared to LAVi in atrial-focused views by 2D TTE (28.3±14.3 vs. 30.4±13.7 ml/m²; p=0.0014) (Figure 1), and both measurements were significantly smaller compared to LAVi measured by 3D TTE (34.4±16.9 ml/m²; p<0.0001 and p=0.0002, respectively) (Figure 2). LAVi assessed by analyses in atrial-focused 2D TTE views was less different from 3D LAVi measurements (ΔLAVi=-4.0 ml/m², 95%CI -6.0 to -2.0; p<0.0001) than LAVi assessed in standard 2D TTE views (ΔLAVi=-6.1 ml/m², 95%CI -7.8 to -4.5; p=0.0002).

In atrial-focused 4-chamber and 2-chamber views length of the LV was smaller (6.0±0.7 cm and 6.0±0.7 cm) compared to length in standard apical 4-chamber and 2-chamber views (6.4±0.9 cm and 6.5±0.7 cm; p=0.0001 and p<0.0001, respectively) by 2D TTE indicating foreshortening of the LV in the LA optimized views.

 

Conclusions: Measurements of LAVi in dedicated atrial-focused views were larger than LAVi assessed in standard 4-chamber and 2-chamber views by 2D TTE. Both 2D TTE measurements of LAVi were significantly smaller than LAVi assessed by 3D TTE as the reference method. Clinical impact of underestimation of LAVi by 2D TTE standard views has to be evaluated in future studies.