Normal ranges of left atrial volumes and ejection fraction by 3D echocardiography in adults: a systematic review and meta-analysis

Increased sizes and dysfunction of the left atrium have been related to adverse outcomes. 3D-echocardiography is more accurate than 2D-echocardiography in estimating LA volumes and ejection fraction. However, the use of 3DE for LA analysis is limited by the absence of established reference values. We performed a systematic review and meta-analysis to provide reference ranges of LA maximum and minimum volumes indexed for body surface area (LAVi max and LAVi min, respectively), and LA-EF assessed by 3DE in healthy adults. Data search was conducted from inception through September 15, 2021, using the following Medical Subject Heading terms: left atrial/atrium, three-dimensional/3D echocardiography. The study protocol was registered in the PROSPERO database (CRD42021252428). 15 studies including 4,226 healthy adults (51% males) and reporting 3DE values of LAVi max, LAVi min and LA-EF were selected. LAVi max, LAVi min and LA-EF mean and reference values were equal to 25.18 ml/m(2) (95% CI 23.10, 27.26), 11.10 ml/m(2) (10.01, 12.18) and 55.94% (51.92, 59.96), respectively. No influential studies were identified. Pooled estimates per age group- and sex were also estimated. By meta-regression analyses, we identified variability in LA volumes and LA-EF depending on participants' age, ethnicity and number of heart cycles at 3D multi-beat acquisition. At individual patient data analysis conducted on 374 subjects, a software effect on LA-EF was shown. This systematic review and meta-analysis provides reference values of LAVi max, LAVi min and LA-EF assessed by 3DE in healthy adults, encouraging 3DE evaluation of the LA evaluation in daily practice.