Differentiating pre-capillary and post-capillary pulmonary hypertension by Doppler echocardiography in a large realworld database

Background: Pulmonary hypertension (PH) is common, dangerous and has multiple causes. Vasodilator therapy has significantly improved the prognosis of patients with pulmonary arterial hypertension (PAH), but the diagnosis can be challenging, requiring right heart catheterisation (RHC). Differentiating pre-capillary PH (prePH) and postcapillary PH (postPH) and measuring pulmonary vascular resistance (PVR) are key steps for diagnosing PAH. A novel echocardiographic parameter, the pulmonary to left atrial ratio (ePLAR), which is derived from the tricuspid regurgitation velocity (TRV) divided by the ratio between the early diastolic filling velocity and the early mitral annulus velocity (E/e’), i.e., ePLAR=TRV/E/e’, has been described as a surrogate for RHC. This retrospective cohort study tests the ability of ePLAR to differentiate prePH and postPH, in a large real world database. Methods: The data from all RHC performed within a 5-year period (January 2010 to February 2015) were extracted from the hospital database. The closest corresponding echocardiograms (echos) were searched in the national echo database Australia (NEDA) using the identifiers from RHC data. The performance of ePLAR in differentiating two PH physiologies was compared against the gold standard RHC using various statistical methods. Results: 887 pairs of echos and RHCs were merged and analysed in our study. The median time difference between RHC and echocardiography was 7 (IQR 1-62) days. The ePLAR was calculable in 184 cases (21%). Median (IQR) ePLAR values were significantly different between prePH and postPH groups: 0.35 (0.13-0.50) m/s vs 0.17 (0.12-0.23) m/s (P=0.003), despite both groups having similar mean pulmonary artery pressures. The optimal ePLAR cut-off of 0.28m/s had a positive predictive value of 94% for postPH, with sensitivity of 83% and specificity of 67%. Conclusions: ePLAR helps to discriminate postPH from prePH and may be useful in evaluating these patients