The Right Atrium and Atrialised Right Ventricle are Associated with Cardiac Output During Exercise in Patients with Ebstein Anomaly of the Tricuspid Valve.

The right atrium (RA) and atrialised RV (aRV) may be important in determining exercise capacity in Ebstein anomaly (EA). We performed exercise testing and resting/exercise cardiac magnetic resonance imaging (CMRI) to examine associations between RA and aRV and left heart volumes, cardiac index and exercise capacity (%VO2max). In 13 un-operated EA patients (median age 13.5 years), indexed end-diastolic volumes were calculated from resting CMRI; right atrium (RAi), atrialised RV (aRVi), functional RV (fRVEDVi), left atrium (LAi) and left ventricle (LVEDVi). Systolic (SCRsys) and diastolic (SCRdias) septal curvature were measured. Pulmonary artery and aortic flow were measured at rest and peak exercise, and cardiac index (CI) calculated. CIex was strongly positively associated with %VO2max (r = 0.74, p = 0.01). RAi and aRVi, but not fRVEDVi, were negatively associated with %VO2max, CIrest and CIex. fRVEF was positively associated with %VO2max, CIrest and CIex. LAi, LVEDVi and LVEF were associated with %VO2max, CIrest and CIex. SCRdias was strongly negatively associated with aRVi (r=-0.89, p < 0.01) and RAi (r=-0.73,p < 0.01) but not with fRVEDVi (r =-0.34,p = 0.28). In multivariable models LVEDVi had the most significant influence on %VO2max, CIrest and CIex. In EA, volumes of the true RA and aRV but not fRV are associated with exercise capacity and cardiac output at rest and on exercise. Maintaining LV diastolic volume is a key determinant of exercise capacity in EA.