Statistical analysis:
Descriptive statistics were summarized as mean ± standard deviation or number with percentage. Statistically relevant correlations between the Doppler echocardiographic parameters and RVEF by CMR were achieved by linear regression analysis. Receiver operating characteristics (ROC) curves were obtained by analyzing the variables of echocardiography as the sample factors and RVEF by CMR as the state variable. Shapiro-Wilk test was made use to determine the normal distribution of data, whereas an analysis of variance (ANOVA) was used to compare amongst the groups of Doppler echocardiographic variables and other demographic variables. As mentioned above, the standard error of estimate of the mean percent signifies inter-observer variability. We used R 3.4.1 (Foundation for Statistical Computing, Vienna, Austria) to run our analysis.