Assessment of the Accuracy and Reproducibility of RV Volume Measurements by CMR in Congenital Heart Disease

Objectives The purpose of this study was to determine whether right ventricular (RV) volumes are more accurately and reproducibly measured by cardiac magnetic resonance (CMR) in an axial orientation or in a short-axis orientation in patients with congenital heart disease (CHD). Background There is little agreement on the most suitable imaging plane for RV volumetric analysis in the setting of abnormal RV physiology. Methods Measurements of RV volumes from datasets acquired in axial and short-axis orientations were made in 50 patients with CHD. RV stroke volumes (SV) calculated using these 2 methods were compared with forward flow measured in the pulmonary trunk by phase contrast (PC) imaging. Repeated volume measurements were made to assess intraobserver and interobserver reliability. Bland-Altman plots and Lin's concordance correlation coefficient (CCC) were used for all analyses of agreement. Results Analysis of all subjects revealed a statistically significant difference in interobserver reliability of RV end-systolic volume (ESV) measurements that favored the axial method (p = 0.047). The magnitude of measurement differences between observers in this case was small (−2.8 ml/m2 ; 95% confidence interval: −5.6 to 0.0). There was no difference between the 2 contouring methods in terms of intraobserver reliability in measurements of RV end-diastolic volume (EDV), ESV, ejection fraction, or SV (p > 0.05 in all cases). In subjects with RV EDV ≥150 ml/m2 , RV SV measured using axial contours yielded better agreement with forward flow measured in the pulmonary trunk (CCC = 0.63) than did measurements made using short-axis contours (CCC = 0.56; p = 0.007). Conclusions Trends favoring the axial orientation in terms of reproducibility were not clinically significant. In subjects with RV EDV ≥150 ml/m2 , the axial orientation yields RV volume measurements that agree more closely with flow measured in the pulmonary trunk than does the short-axis orientation.