Background-Quantitative assessment of ventricular volumes and mass in pediatric patients with single-ventricle physiology would aid clinical management, but it is difficult to obtain with 2-dimensional echocardiography. The purpose of the present study was to compare matrix-array 3-dimensional echocardiography (3DE) measurements of single-ventricle volumes, mass, and ejection fraction with those measured by cardiac magnetic resonance (CMR) in young patients. Methods and Results-Twenty-nine patients (median age, 7 months) with a functional single ventricle undergoing CMR under general anesthesia were prospectively enrolled. The 3DE images were acquired at the conclusion of the CMR. Twenty-seven of 29 3DE data sets (93%) were optimal for 3DE assessment. Two blinded and independent observers performed 3DE measurements of volume, mass, and ejection fraction. The 3DE end-diastolic volume correlated well (rϭ0.96) but was smaller than CMR by 9% (PϽ0.01), and 3DE ejection fraction was smaller than CMR by 11% (PϽ0.01). There was no significant difference in measurements of end-systolic volume and mass. The 3DE interobserver differences for mass and volumes were not significant except for ejection fraction (8% difference; PϽ0.05). Intraobserver differences were not significant. Conclusions-In young pediatric patients with a functional single ventricle, matrix-array 3DE measurements of mass and volumes compare well with those obtained by CMR. 3DE will provide an important modality for the serial analysis of ventricular size and performance in young patients with functional single ventricles.

Our hypothesis was that the relationship between the internal aortic diameter and the Doppler flow velocity across the aortic isthmus could be modeled by applying the principle of conservation of mass flow. The aortic diameter decreased at the isthmus by a mean of 18% (t = 11.02, p < 0.0001), while the flow velocity increased by a mean of 44% (t = 10.09, p < 0.0001). The mean peak mass flow rate was 34.5 ml/s preisthmus and 32.9 ml/s at the isthmus with excellent correlation (r = 0.830). We conclude that the increase in Doppler velocity observed in the descending aorta can be explained by the normal narrowing observed at the aortic isthmus and application of the continuity equation for conservation of mass flow.

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