Prognostic Value of Right Ventricular Ejection Fraction Assessed by Transthoracic 3D Echocardiography

Background - Cardiac magnetic resonance is the gold standard for the evaluation of right ventricular (RV) volumes, but it is impractical to perform in every patient. Although reference values of RV volumes and RV ejection fraction by 3D transthoracic echocardiography (3DTTE) have been established, their prognostic values have not been elucidated yet. We hypothesized that RV ejection fraction measured by 3DTTE (3DRVEF) predicts future cardiovascular events. Methods and Results - In protocol 1, we determined the accuracy of RV volumes and RV ejection fraction measurements by 3DTTE against cardiac magnetic resonance in 60 subjects. In protocol 2, 3DRVEF was measured in 446 patients with various cardiovascular diseases. Study subjects were followed up to record cardiac death and major adverse cardiovascular events. In protocol 1, 3DTTE-determined RV end-diastolic volume, end-systolic volume, and RV ejection fraction had good correlations to those by cardiac magnetic resonance (r=0.74-0.90). In protocol 2, 38 cardiac deaths and 88 major adverse cardiovascular events occurred during a median follow-up of 4.1 years. Univariable Cox proportional analysis revealed that 3DRVEF was associated with both cardiac death (P<0.0001) and major adverse cardiovascular event (P<0.0001). 3DRVEF remained as an independent predictor for cardiac death (P<0.0001) and major adverse cardiovascular event (P<0.0001) even in a stepwise multivariable Cox proportional hazard analysis. Classification and regression-tree analysis demonstrated that 3DRVEF played an important role for risk stratification. Conclusions - 3DTTE-determined RV ejection fraction was independently associated with cardiac outcomes in patients with diverse backgrounds. 3DRVEF offered incremental value over clinical risk factors and the other echocardiographic parameters including left ventricular systolic and diastolic function for predicting future adverse outcome.