Right Ventricular Myocardial Isovolumic Relaxation Time as Novel Method for Evaluation of Pulmonary Hypertension: Correlation with Endothelin-1 Levels

Abstract

Noninvasive assessment of pulmonary artery systolic pressure (PASP) has several limitations. Right ventricular (RV) isovolumic relaxation time (IVRT) is sensitive to changes in PASP. Blood pool-derived RV IVRT correlates well with PASP. However, because of complex parameter derivation, the method is rarely used. Endothelin (ET)-1 levels are elevated in congestive heart failure in relation with the severity of pulmonary hypertension. We sought to validate the measurement of pulsed wave (PW) Doppler tissue imaging (DTI)-derived myocardial RV IVRT as a predictor of PASP against invasively measured PASP and correlate this with ET-1 levels. This study enrolled 53 patients with pulmonary hypertension and 20 age- and sex-matched healthy individuals as a control group. Transthoracic echocardiography with DTI and assessment of plasma level of ET-1 were performed just before right heart catheterization. PW DTI and M-mode echocardiography were used for assessment of tricuspid annular systolic motion. Ejection fraction of RV was estimated by Simpson's rule. Blood pool-derived IVRT and PW DTI-derived IVRT were estimated and corrected for heart rate (IVRTc). Echocardiographically derived PASP, myocardial PW DTI-derived IVRTc, blood pool-derived IVRTc, and ET-1 levels were significantly higher in patients than in control subjects (68.66 +/- 21.88 vs 18.78 +/- 7.47 mm Hg, 121.75 +/- 49.11 vs 28.33 +/- 25.1 milliseconds, 77.21 +/- 42.66 vs 26.79 +/- 19.85 milliseconds, and 7.04 +/- 2.45 vs 1.35 +/- 1.12 pg/mL, respectively, P < .001 for all). A strong positive correlation was found between invasively measured PASP and PW DTI-derived IVRTc (r = .86), blood pool-derived IVRTc (r = .75), and ET-1 level (r = .94), and between PW DTI-derived IVRTc and ET-1 levels (r = .82), whereas strong negative correlation was detected between ET-1 levels and both RV ejection fraction (r = -.73) and RV Tei index (r = -.73, P < .001 for all correlations). Tricuspid annular PW DTI-derived IVRTc correlates very strongly with both invasively measured PASP and ET-1 levels. Therefore, it can be used to predict PASP. It can even be considered as an alternative to tricuspid regurgitation-derived PASP when tricuspid regurgitation is nonrecordable. However, caution should be taken while examining patients with significantly reduced RV function.