Objectives .– The aim of this study was to assess right ventricular (RV) ejection fraction (EF) and its determinants in patients with organic mitral regurgitation (MR) by radionuclide angiography.

Methods .– Two-hundred eight patients (62 ± 13 years, 135 males) with moderate to severe organic MR underwent an echocardiographic examination and left and right ventricular assessment by radionuclide angiography. The left ventricle (LV) was divided into 9 regions to assess regional LV function.

Results .– Mean RV EF was 40 ± 10%, ranging from 10 to 65%. One hundred fifty-one patients were in sinus rhythm, and 57 patients (27%) in atrial fibrillation. Tricuspid annulus S wave velocity measured in a subset of patients ( n = 92) correlated weakly with RV EF ( r = 0.27, P = 0.018). Fifty-nine patients (28%) had a RV EF < 35%. Patients with RV EF < 35% had lower systolic blood pressure ( P = 0.045), larger RV ( P = 0.007), higher pulmonary artery systolic pressure (PASP, P = 0.045) and had more diuretics ( P = 0.009) compared with those with RV EF > 35%. In univariate analysis, echocardiographic predictors of RVEF were LVEF ( r = 0.33, P < 0.0001), LV end-diastolic diameter ( r = −0.26, P = 0.001) and volume ( r = −0.29, P = 0.001), left atrial size ( r = −0.22, P = 0.003), mitral E velocity ( r = −0.29, P < 0.0001), PASP ( r = −0.22, P = 0.004), and aortic stroke volume ( r = 0.31, P = 0.007). In the subset of patients with effective regurgitant orifice (ERO) and regurgitant volume quantification RV EF correlated with ERO ( r = −0.34, P = 0.005) and regurgitant volume ( r = −0.33, P = 0.008). RV EF correlated closely with radionuclide LV septal function (regional LV EF 8: r = 0.49, P < 0.0001). In multivariate analysis, LV septal function ( r = 0.43, P < 0.0001) was the main determinant of RV function. LV end-diastolic diameter ( r = −0.25, P < 0.0001) and PASP ( r = −0.18, P = 0.009) were also independent predictors of RVEF.

Conclusion .– In organic mitral regurgitation RV function depends not only on PASP but also on LV remodeling and septal function.