Evaluation of stroke volume and ventricular mass in a fetal heart model: A novel four-dimensional echocardiographic analysis

Aims: This study aimed to assess the feasibility and accuracy of nongated four-dimensional echocardiography (4DE) for determining left ventricular (LV) stroke volume (SV) and mass in a fetal heart-sized LV model. Methods: A balloon was inserted into the LV of 20 fresh rabbit hearts and attached to a calibrated pulsatile pump. Ten hearts retaining the right ventricle were imaged in Group A. Ten hearts without the right ventricles (RVs) attached were imaged in Group B. Nongated 4D volumes were obtained using a Philips iU-22 system with an X6-1 matrix probe at SVs ranging from 1 to 5 mL at increments of 1 mL. At each SV, the volume displacement of the heart was measured at end-systole and end-diastole. Mass was determined by displacement at the conclusion of the experiment. Results: The images were analyzed offline by manually tracing endocardial and epicardial boundaries of stacked contours. An excellent correlation in SV and mass between echo-derived values and displacement values was demonstrated and accompanied by high coefficients of determination (R2) in both groups (SV: Group A: R² = 0.9461, Group B: R² = 0.9811; Mass: Group A: R² = 0.9223, Group B: R² = 0.9602; all P < 0.001). Bland-Altman analyses showed a slight overestimation in both groups for both SV and LV mass. Conclusions: Nongated 4DE was demonstrated to be feasible and that it could accurately define SV and ventricular mass for a fetal heart-sized LV model. (Echocardiography 2014;31:1138-1145).