P6093D echocardiography versus cardiovascular magnetic resonance in the evaluation of the right ventricle in patients with congenital heart disease after pulmonary valve replacement

Background Cardiac MR (CMR) is the gold standard for right ventricular (RV) quantification. Three-dimensional echo (3DE) is a relatively new technique which may offer a rapid alternative for the examination of the right heart. The purpose of this study was to investigate the clinical significance and interchangeability of these modalities to evaluate patients with congenital heart disease (CHD) who underwent percutaneous pulmonary valve implantation (PPVI) for RV outflow tract dysfunction. Methods 36 patients who underwent PPVI were evaluated with 3DE and CMR to quantify the RV. RV volumes and ejection fraction (EF) were measured for both imaging techniques with commercially available softwares (Tomtec-Germany for 3DE and Medimatic-Netherlands for CMR data). Paired t-test, Bland-Altman analysis, and Pearson's correlation analysis were used as most appropriate to compare both measured techniques with CMR regarded as the reference standard. Results 86% of the patients (31 patients) had adequate image quality on 3DE and was included in the study. Patients underwent both 3D echo and CMR within a mean of 9 days of each other and at a mean time of 3 years after PPVI. Compared to CMR, 3D echo significantly underestimated volumes in all patients and overestimate RV ejection fraction (EF). Mean RV End-diastolic Volumes (EDV) and End-Systolic Volumes (ESV) were significantly greater when measured by CMR compared to 3D echo (EDV: 99 ml/m2 vs. 85 ml/m2; p<0.01, ESV: 52 ml/m2 vs. 41 ml/m2; p<0.01). Mean RV EF was lower when measured by CMR compared to 3D echo (48% vs 52%; p<0.05). Linear regression analysis showed high correlation coefficients between 3DE and CMR (r=0,68 for EDV, r=0,62 for ESV, and r=0,57 for EF; p<0.001). Bland-Altman analysis demonstrated that for both RV EDV and RV ESV there was a significant and systematic under-estimation of volume by 3D echo compared to CMR. Both 3DE and CMR measurements were found to be highly reproducible in terms of intra-observer variability. Conclusions Statistically significant and clinically meaningful differences in volumetric measurements were observed between 3DE and CMR in the evaluation of RV volumes and function in patients with CHD after PPVI. Despite linear regression and Bland-Altman analysis showed that the two techniques are related and present some degree of agreement, 3D Echocardiography systematically underestimates volumes and overestimates EF and this would have to be considered in the clinical practice.