The Total Right/Left-Volume Index: A New and Simplified Cardiac Magnetic Resonance Measure to Evaluate the Severity of Ebstein Anomaly of the Tricuspid Valve

BACKGROUND: The classification of clinical severity of Ebstein anomaly still remains a challenge. The aim of this study was to focus on the interaction of the pathologically altered right heart with the anatomically-supposedly-normal left heart and to derive from cardiac magnetic resonance (CMR) a simple imaging measure for the clinical severity of Ebstein anomaly. METHODS AND RESULTS: Twenty-five patients at a mean age of 26±14 years with unrepaired Ebstein anomaly were examined in a prospective study. Disease severity was classified using CMR volumes and functional measurements in comparison with heart failure markers from clinical data, ECG, laboratory and cardiopulmonary exercise testing, and echocardiography. All examinations were completed within 24 hours. A total right/left-volume index was defined from end-diastolic volume measurements in CMR: total right/left-volume index=(RA+aRV+fRV)/(LA+LV). Mean total right/left-volume index was 2.6±1.7 (normal values: 1.1±0.1). This new total right/left-volume index correlated with almost all clinically used biomarkers of heart failure: brain natriuretic peptide (r=0.691; P=0.0003), QRS (r=0.432; P=0.039), peak oxygen consumption/kg (r=-0.479; P=0.024), ventilatory response to carbon dioxide production at anaerobic threshold (r=0.426; P=0.048), the severity of tricuspid regurgitation (r=0.692; P=0.009), tricuspid valve offset (r=0.583; P=0.004), and tricuspid annular plane systolic excursion (r=0.554; P=0.006). Previously described severity indices (RA+aRV/fRV+LA+LV) and fRV/LV end-diastolic volume corresponded only to some parameters. CONCLUSIONS: In patients with Ebstein anomaly, the easily acquired index of right-sided to left-sided heart volumes from CMR correlated well with established heart failure markers. Our data suggest that the total right/left-volume index should be used as a new and simplified CMR measure, allowing more accurate assessment of disease severity than previously described scoring systems.