RV Volumetry—From Simple 2D TTE Measurements to a Complex Form

Background: Accurate assessment of right ventricular (RV) volume is crucial for monitoring patients with congenital heart defects (CHDs). However, due to the RV’s complex geometry, transthoracic echocardiography (TTE) is challenging, and MRI is commonly used to evaluate RV volume. Despite its accuracy, MRI has several limitations: it lacks bedside imaging, is time-consuming, costly, and often requires sedation in CHD patients. Therefore, this study aimed to develop a reliable, simple, and quick method for calculating RV volume using 2D TTE.

Methods: A retrospective, single-center study was conducted at the DHZC Berlin. Standard apical four-chamber (4CH) and parasternal short-axis (PSAX) views were obtained using 2D TTE in patients with CHD during routine follow-up. RV volumes were calculated using the conventional ellipsoidal shell model formula and a novel approach based on a cone model. The results from both methods were compared with RV volumes obtained via MRI.

Results: Forty CHD patients (15 female) with a median age of 20.01 years were included in the study. The traditional 2D TTE approach for RV volume quantification relies on the 2/3 * S′ * a ellipsoid formula (S′ = RV area in 4CH; a = distance anterior tricuspid valve annulus to anterior pulmonary valve annulus in PSAX). We propose an alternative method using a cone-based formula: (2/3) * (S * S′/d + [π * d * S′/8]), (S′ = RV area; d = tricuspid valve annulus diameter in 4CH; S = RV area in PSAX). This approach demonstrated superior performance with a significantly reduced y-axis value (2.5/25.45 systolic/diastolic) compared with the ellipsoid model (12.65/37.73 systolic/diastolic), maintaining comparable correlations (r = 0.95/0.92 systolic/diastolic) with the cone model versus (r = 0.91/0.9 systolic/diastolic) with the ellipsoid formula. Based on the root mean square error (RMSE), which is the most appropriate measure of fit under the assumption of model linearity, our cone model (RMSE 13.17/28.35 systolic/diastolic) demonstrates significantly better predictive accuracy than the conventional ellipsoid model (RMSE 20.84/52.55 systolic/diastolic). The mean difference from MRI-measured systolic/diastolic volumes was 9.3/19.2 mL (11.1/11.6%) with the cone model, compared with 13.9/40.4 mL (19.9/26.7%) with the ellipsoid formula.

Conclusion: The proposed method shows excellent alignment with the data, as indicated by the low y-axis intercept and RSME, while maintaining a strong correlation with MRI measurements. This promising approach offers a feasible, accurate, and rapid method for bedside assessment of RV volume, enhancing prompt and precise clinical decision-making.

Publication History

Article published online:
11 February 2025