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Background: Traditional echocardiographic methods used for evaluation of pulmonary hypertension (PH) have several limitations. Right ventricular (RV) isovolumic relaxation time (IVRT) ) is sensitive to changes in pulmonary artery systolic pressure (PASP). Plasma endothelin-1 (ET-1) levels are elevated patients with PH & correlates with PH severity.Objectives: To test hypothesis of measurement of Pulsed-wave Doppler tissue imaging (PWDTI)-derived RV myocardial IVRT as a valid predictor of PASP against invasively measured PASP & correlate this with ET-1 levels.Patients & Methods: The study included 94 patients with PH with different cardiac pathologies & 30 healthy subjects as a control group. Conventional echocardiography with DTI & assessment of plasma level of ET-1 were performed just before invasive measurement of PASP. Tricuspid annular motion at RV free wall was assessed by M-mode echocardiography & PWDTI. Blood pool-derived IVRT & PWDTI-derived IVRT were estimated & corrected for heart rate (IVRTc).Results: Echo-derived PASP, RV Tei index and ET-1 levels were significantly higher in patients than controls (69.57±23.06 mm Hg vs.18.6±4.26 mm Hg,1.19±0.42 vs.0.43±0.12,6.9±0.99 pg/ml vs. 1.45 ± 0.46 pg/ml, respectively, p<0.001 for all). Tricuspid annular plane systolic excursion was significantly lower in patients than controls (17.76±6.17 mm vs.27.9± 6.04 mm, p<0.05). Myocardial PWDTI-derived IVRTc, myocardial PWDTI-derived IVRT (non corrected)& blood pool-derived IVRTc were significantly higher in patients than controls (90.51±31.77 ms vs. 23.63±4.73 ms,85.87±29.19 ms vs. 18.49±3.45 ms, 82.33±22.13 ms vs. 15.11±5.09 ms, respectively, p<0.001 for all). Strong positive correlations found between invasively measured PASP & each of myocardial PWDTI-derived IVRTc ( r =.82),myocardial PWDTI-derived IVRT( r =.79),blood pool-derived IVRTc ( r =.67),RV Tei index ( r = .61), ET-1 level ( r =.78) also between PWDTI-derived IVRTc & ET-1 levels ( r =.75), P<0.001 for all correlations. The cutoff point of RV myocardial IVRT is 65 ms & for RV myocardial IVRTc is 70 ms, for prediction of PASP >40 mmHg,with 93% & 96% sensitivity,90 % & 94% specificity, respectively.Conclusion: PWDTI-derived RV myocardial IVRTc measured at the tricuspid annulus of RV free wall correlates very strongly with both invasively measured PASP & ET-1 levels therefore, can be used to predict PASP. It can be used as a complementary echocardiographic method for prediction of PASP or as an alternative method when tricuspid regurgitation is non recordable or difficult to measure.