Reference Values of Right Ventricular Volumes and Ejection Fraction by Three-Dimensional Echocardiography in Adults: A Systematic Review and Meta-Analysis

Objective: This study was conducted in order to determine the reference values for right ventricular (RV) volumes and ejection fraction (EF) using three-dimensional echocardiography (3DE) and to identify sources of variance through a systematic review and meta-analysis. Methods: This systematic review was preregistered with the International Prospective Register of Systematic Reviews (https://www.crd.york.ac.uk/PROSPERO/) (CRD42020211002). Relevant studies were identified by searches of the PubMed, Embase, and Cochrane Library databases through October 12, 2020. Pooled reference values were calculated using the random-effects model weighted by inverse variance. Meta-regression analysis and Egger's test were used to determine the source of heterogeneity. A subgroup analysis was performed to evaluate the reference values across different conditions. Results: The search identified 25 studies of 2,165 subjects. The mean reference values were as follows: RV end-diastolic volume, 100.71 ml [95% confidence interval (CI), 90.92–110.51 ml); RV end-systolic volume, 44.19 ml (95% CI, 39.05–49.33 ml); RV end-diastolic volume indexed, 57.01 ml/m(2) (95% CI, 51.93–62.08 ml/m(2)); RV end-systolic volume indexed, 25.41 ml/m(2) (95% CI, 22.58–28.24 ml/m(2)); and RVEF, 56.20% (95% CI, 54.59–57.82%). The sex- and age-specific reference values were assessed according to the studies reporting the values of different sexes and age distributions, respectively. In addition, the vendor- and software-specific reference values were analyzed. The meta-regression analysis revealed that sex, frame rate, pulmonary artery systolic pressure, and software packages were associated with variations in RV volumes (P < 0.05). Inter-vendor and inter-software discrepancies may explain the variability of RVEF. Conclusions: The reference values for RV volumes and RVEF using 3DE were assessed. The confounders that impacted the variability in RV volumes or RVEF contained the sex, frame rate, pulmonary artery systolic pressure, inter-vendor discrepancies, and inter-software discrepancies.