Background: Adult studies have demonstrated that three-dimensional echo (3DE) quantification of MR is equivalent to MRI, and superior to two-dimensional echo (2DE), however the mechanisms of MR in adults differ considerably from pediatrics. There are no studies to date assessing the feasibility & precision of 3DE in quantifying MR in children. This pilot study aims to compare the accuracy of 2DE & 3DE to the reference standard of MRI in quantifying MR.
Method: Children with MR were prospectively recruited for cardiac MRI and transthoracic 2DE & 3DE on the same day. Mitral valve effective regurgitant orifice area (EROA) and regurgitant volume (Rvol) were measured with 2DE & 3DE. 2DE EROA was estimated from biplane vena contracta area and PISA method, using parasternal long axis & 4-chamber views. 3DE EROA was calculated from vena contracta area, using planimetry from 3DE color Doppler and multiplanar reconstruction. 2DE & 3DE Rvol was calculated as EROA x MR velocity time integral. MRI Rvol was the difference between left ventricular stroke volume and aortic flow. 2DE & 3DE were compared to MRI using Pearson correlation and Bland-Altman.
Result: Fifteen patients were enrolled, 1 was excluded for poor-quality MRI. Of the 14 patients included (9 - 18y); 4 had mild MR and 10 had moderate or greater MR. 3DE Rvol (r=0.86, p<0.0001) and 3DE EROA (r=0.84, p=0.0002) had a strong correlation with MRI Rvol. 3DE EROA also had a moderate correlation with MRI LV end diastolic volume (r=0.63, p=0.01). 2DE EROA by parasternal long axis PISA (r=0.60, p=0.02) and 4-chamber PISA (r=0.60, p=0.02) had a moderate correlation with MRI Rvol, and 2DE EROA by biplane vena contracta area (r=0.10) had no correlation. 3DE overestimated Rvol by 5.5% compared with MRI. 2DE overestimated Rvol by 11-20% relative to 3DE and 17-27% relative to MRI. Bland-Altman had a close agreement between 3DE and MRI Rvol (bias -2.3 +/- 9.7, limits -21.2 to 16.7).
Conclusion: Quantification of MR Rvol by 3DE in children is feasible and closely correlates to MRI. Overestimation of Rvol by 2DE may reflect the more eccentric and elliptical shape of the vena contracta in the pediatric population. 3DE can quantify the degree of MR and assess the progression of MR, which may improve our ability to stratify children for surgical repair.