Resident Cornell University Ithaca, New York, United States
Abstract: Background – Determining right ventricular (RV) volume typically requires three-dimensional imaging due to its complex shape. The crescentic ellipsoid model (CEM) offers a two-dimensional alternative, employing area- or linear-based formulas (Figure 1) with further variations based on echocardiographic views (Figure 2).
Hypothesis/Objectives – To identify which CEM variant best agrees with real-time three-dimensional echocardiography (RT3D) as a reference standard and to assess within-day reproducibility.
Animals – Sixty-seven client-owned dogs (23 normal, 44 with right-sided heart diseases) underwent echocardiograms, with 20 normal dogs receiving a repeat exam.
Methods – Prospective method comparison study. Body weight-indexed end-diastolic (iEDV) and end-systolic volumes (iESV) were calculated across eight CEM variants. Agreement with RT3D was assessed using concordance correlation coefficients (rc) and Bland-Altman analysis, while within-day reproducibility was evaluated using intraclass correlation coefficients (ICC) and reproducibility coefficients.
Results – The area- and linear-based CEMs using RV parameters from the left apical four-chamber view and cardiac diameter from the right parasternal short-axis view (CEM_A4C-RPS and LCEM_A4C-RPS, respectively) were the only methods to achieve moderate agreement with RT3D (rc >0.90). The CEM_A4C-RPS showed no significant systematic bias for iEDV (median of the differences [95% confidence interval]: 0.09 [0.00–0.13]), while LCEM_A4C-RPS displayed no significant systematic bias for iEDV (0.03 [-0.02–0.08]) and iESV (0.04 [-0.01–0.12]). Both methods demonstrated good reproducibility for iEDV and iESV (ICC >0.75), with iESV reproducibility significantly greater than that of methods using RV parameters from the right parasternal long-axis view.
Conclusions and Clinical Importance – The CEM_A4C-RPS and LCEM_A4C-RPS provide clinically practical RV volume estimates.
