Potential of cardio-thoracic ratio measured on chest radiography for the prediction of pulmonary hypertension: Correlation with pulmonary arterial systolic pressure estimated by echocardiography

Background Currently, there are no data on the association between pulmonary hypertension and chest radiography changes specific for idiopathic pulmonary arterial hypertension in lupus. Therefore, we aimed to assessthe correlation of cardio-thoracic (CT) ratiomeasured by chest radiography for predicting pulmonary hypertension estimated by echocardiography in lupus patients. Objectives This study aims to determine whether CT ratio is increased in lupus patients with pulmonary hypertesion and its correlation with disease activity and other parameters. Methods 105 patients (median 42.75±2.14 years; 10 male) who had undergone chest radiography and echocardiography were divided into two groups (hypertensive and normotensive) based upon an echocardiography-derived pulmonary arterial systolic pressure (PASP) of 25 mmHg. CT ratio was measured twice. 1st CT ratio was calculated at the time of enrolled trial and 2nd CT ratio was calculated after two years later. Difference between 1st and 2nd measured CT ratio, 1st CT ratio and 2nd CT ratio were then correlated with PASP using regression analysis. The Area Under the Curve (AUC) for predicting pulmonary hypertension on CT ratio was calculated. Results In the pulmonary hypertensive group, the mean PASP was 53.13±7.76 mmHg (39-104 mmHg) and there was statistical strong correlation between the increased 2nd cardiothoracic ratios and PASP (OR=0.228 p=0.002) but, not correlation with 1st cardiothoracic ratio (OR=-0.055 p=0.462) and difference between 1st and 2nd CT ratio (OR=0.044 p=0.472). Interstitial lung disease in lupus patients were associated with PASP (OR=0.277 p=0.002) statistically. The intraobserver and interobserver correlation coefficients for cardiothoracic ratios were 0.990 and 0.892. The AUC for predicting pulmonary hypertension over 25 mmHg by echocardiography was 0.668 in 1st CT ratio (P>0.05), 0.918 in 2nd CT ratio and 0.919 in difference between 1st and 2nd CT ratio (P<0.05). Conclusions Increased CT ratios of chest radiography was correlated statistically well with PASP estimated by echocardiography and could be used to predict pulmonary hypertension over 25 mmHg with high sensitivity and specificity. .