3D Echo Underestimates Right Heart Volumes, Matches Ejection Fraction

A comprehensive systematic review and meta-analysis published in Echo Research & Practice has evaluated the accuracy of three-dimensional echocardiography (3DE) in measuring right ventricular (RV) volumes and ejection fraction (EF) compared to cardiac magnetic resonance imaging (CMR). The study, conducted by researchers including Mostafa Rafea, Ramy Kishk, and Ramy Salmoun, synthesized data from 75 studies encompassing approximately 4,300 patients to determine whether 3DE can serve as a reliable alternative to the reference standard of CMR for assessing right heart function. The central finding indicates that while 3DE systematically underestimates right ventricular volumes, it demonstrates minimal and statistically non-significant bias when measuring ejection fraction, suggesting a specific utility for functional assessment over precise volumetric quantification.

Although 2D echocardiography remains the most commonly used technique in the assessment of RV function, it is challenging and is capable of measuring only surrogate parameters due to the complex ventricular geometry. However, CMR is often limited by availability, cost, and the potential need for anesthesia in pediatric populations, creating a clinical need for a faster, more accessible tool that aligns closely with CMR results.

The researchers conducted a systematic literature review of PubMed, Embase, and the Cochrane Library through December 2024. The study protocol was registered on PROSPERO, and the analysis was reported in accordance with PRISMA guidelines. The inclusion criteria required studies to directly compare 3DE and CMR measurements of RV function and volumes, using 3DE as the index test and CMR as the reference standard. The cohort included both adult and pediatric populations, as well as patients with various cardiac conditions such as heart failure, pulmonary hypertension, congenital heart diseases, and postoperative states.

Methodologically, the team used RevMan Web software with a random-effects model to account for study heterogeneity. For RV volumes, they calculated the standardized mean difference (SMD) with 95% confidence intervals because studies used different units, such as milliliters versus milliliters per square meter of body surface area. For ejection fraction, they used the mean difference (MD) since the units were consistent across studies. The quality of the included studies was assessed using the QUADAS-2 tool, which revealed that the majority of the studies demonstrated good methodological quality with a low risk of bias across all domains and minimal applicability concerns.

The meta-analysis revealed that 3DE consistently underestimated both end-diastolic volume (EDV) and end-systolic volume (ESV) compared to CMR. The underestimation was statistically significant for both parameters, with p-values less than or equal to 0.00001. The greatest underestimation was observed for EDV, with an SMD of −0.43 (95% CI: −0.55, −0.30) across 74 studies. For ESV, the SMD was −0.27 (95% CI: −0.39, −0.16) across 71 studies. In non-indexed terms, this translated to a mean difference of −18.56 ml for EDV and −8.14 ml for ESV. This systematic bias suggests that 3DE may not be suitable for precise volumetric measurements where absolute accuracy is critical.

In contrast, the assessment of right ventricular ejection fraction showed much better agreement between the two modalities. The meta-analysis found a minimal underestimation of EF by 3DE, with a mean difference of −0.92% (95% CI: −2.20, 0.36) across 75 studies. This difference was not statistically significant (p = 0.16), indicating that 3DE provides a reliable estimate of RV ejection fraction. The pooled correlation coefficients further supported this finding, showing a strong positive correlation between 3DE and CMR for EF (0.79, 95% CI: 0.76–0.82), as well as for EDV (0.88) and ESV (0.89).

Subgroup analyses were conducted to explore the sources of heterogeneity and identify factors influencing measurement accuracy. The analysis by age group showed that pediatric patients demonstrated smaller measurement bias compared to adults, likely due to better acoustic windows and simpler cardiac geometry. For ejection fraction, there was no statistically significant difference between the pediatric and adult subgroups. Regarding endocardial tracking methods, semi-automatic tracking provided the closest agreement for EF assessment, with confidence intervals crossing zero, indicating no significant systematic bias. Manual tracking demonstrated the most consistent results for EF, while automatic tracking showed the smallest bias for volume parameters. These findings highlight the importance of operator input and algorithm selection in achieving accurate measurements.

The study also examined the impact of cardiac function status on measurement accuracy. Patients with normal hearts showed the largest underestimation for EF, with a mean difference of −2.12% (p = 0.0008). Conversely, patients with diseased hearts demonstrated better agreement between modalities. This difference may be attributed to larger chamber sizes and more distinct anatomical landmarks in diseased hearts, which facilitate more accurate 3DE measurements. The persistence of substantial heterogeneity across all parameters, with I-squared values ranging from 82% to 90%, indicates that technical and methodological differences between studies contribute significantly to the variability in results. Meta-regression analysis failed to identify mean age, sample size, or year of publication as significant moderators of this heterogeneity.

Comparing these results with previous literature, the findings align with earlier meta-analyses that identified systematic RV volume underestimation by 3DE. However, this study highlights important advances in technology. While a 2010 meta-analysis by Shimada et al. found significant EF underestimation, the current analysis demonstrates non-significant EF bias, suggesting meaningful improvements in EF assessment accuracy over the past decade and a half. Similarly, a 2023 study by Kitano et al. found that 3DE underestimated RVEF by 1.5%, whereas the current meta-analysis found a non-significant bias of −0.92%. These trends suggest that technological advances in 3DE software and hardware have enhanced functional agreement over time, even as systematic volume underestimation persists.

The authors acknowledge several limitations of the study. The included studies used a wide range of 3D echocardiography devices and software over more than two decades, introducing technical heterogeneity that could not be fully accounted for. There was also a high degree of intersubject variability, encompassing patients with diverse cardiac pathologies and healthy volunteers, which may have affected measurement accuracies and limited the generalizability of pooled estimates to specific clinical subgroups. Furthermore, although 75 studies were included, they represented approximately 4,300 participants spread across many small samples rather than large, consistent cohorts, which may introduce uncertainty in the pooled results. Publication bias was assessed using funnel plots and Egger’s test, which indicated minimal bias across all parameters.

Despite these limitations, the consistency of the findings across various subgroups supports the robustness of the main conclusions. The direction of bias was uniform, with volume underestimation observed in all analyses, and RVEF showed minimal bias across all subgroups. The authors conclude that while 3DE may provide acceptable EF measurements for longitudinal assessment in centers with established protocols and experienced operators, it cannot yet replace CMR for precise volume measurements.

The clinical implications of these findings are significant for the management of cardiovascular conditions where RV function is a strong prognostic indicator. The study underscores the continued importance of CMR as the reference standard for precise volumetric assessment while highlighting the growing role of 3DE in functional cardiac evaluation.

Broader clinical adoption of 3DE for right ventricular assessment requires greater standardization of image acquisition, analysis, and reporting. The substantial heterogeneity observed in the meta-analysis reflects real and meaningful technical and methodological differences between studies, such as vendor-specific software algorithms, acquisition protocols, and operator experience. Addressing these variations through standardized protocols and training could enhance the reliability of 3DE and facilitate its integration into routine clinical practice. Until such standardization is achieved, CMR remains the preferred modality for precise quantitative assessment of the right ventricle, while 3DE serves as a valuable complementary tool for functional monitoring.

Subject of Research: Accuracy of 3-dimensional echocardiography versus cardiac magnetic resonance for right ventricular assessment

Article Title: Accuracy of 3-dimensional echocardiography in measuring right ventricular volumes and ejection fraction: a systematic review and meta-analysis

Article References: Rafea, M., Kishk, R., & Salmoun, R. (2026). Accuracy of 3-dimensional echocardiography in measuring right ventricular volumes and ejection fraction: a systematic review and meta-analysis. Echo Research & Practice, 13(1), Article 3. https://doi.org/10.1186/s44156-026-00102-w

Image Credits: AI Generated

DOI: 10.1186/s44156-026-00102-w

Keywords: 3D echocardiography, cardiac magnetic resonance, right ventricle, ejection fraction, meta-analysis, cardiovascular imaging, systematic review, heart function, Accuracy, dimensional, echocardiography, measuring