Abstract
Several echocardiographic methods to estimate pulmonary vascular resistance (PVR) have been proposed. So far, most studies have focused on relatively low PVR in patients with a nonspecific type of pulmonary hypertension. We aimed to clarify the clinical usefulness of a new echocardiographic index for evaluating markedly elevated PVR in chronic thromboembolic pulmonary hypertension (CTEPH). We studied 127 CTEPH patients. We estimated the systolic and mean pulmonary artery pressure using echocardiography (sPAP(Echo), mPAP(Echo)) and measured the left ventricular internal diameter at end diastole (LVIDd). sPAP(Echo)/LVIDd and mPAP(Echo)/LVIDd were then correlated with invasive PVR. Using receiver operating characteristic curve analysis, a cutoff value for the index was generated to identify patients with PVR > 1000 dyn·s·cm(-5). We analyzed pre- and postoperative hemodynamics and echocardiographic data in 49 patients who underwent pulmonary endarterectomy (PEA). In this study, mPAP(Echo)/LVIDd moderately correlated with PVR (r = 0.51, p < 0.0001). There was a better correlation between PVR and sPAP(Echo)/LVIDd (r = 0.61, p < 0.0001). sPAP(Echo)/LVIDd ≥ 1.94 had an 77.1% sensitivity and 75.4% specificity to determine PVR > 1000 dyn·s·cm(-5) (area under curve = 0.804, p < 0.0001, 95% confidence interval [CI], 0.66-0.90). DeLong's method showed there was a statistically significant difference between sPAP(Echo)/LVIDd with tricuspid regurgitation velocity(2)/velocity-time integral of the right ventricular outflow tract (difference between areas 0.14, 95% CI, 0.00-0.27). The sPAP(Echo)/LVIDd and mPAP(Echo)/LVIDd significantly decreased after PEA (both p < 0.0001). The sPAP(Echo)/LVIDd and mPAP(Echo)/LVIDd reduction rate (ΔsPAP(Echo)/LVIDd and ΔmPAP(Echo)/LVIDd) was significantly correlated with PVR reduction rate (ΔPVR), respectively (r = 0.58, p < 0.01; r = 0.69, p < 0.05). In conclusion, the index of sPAP(Echo)/LVIDd could be a simpler and reliable method in estimating CTEPH with markedly elevated PVR and also be a convenient method of estimating PVR both before and after PEA.