2018 proceedings from the 6^th world symposium on pulmonary arterial hypertension (PAH) reinforces the 2015 ESC/ERS guidelines for risk stratification identifying patients with low risk clinical worsening or death from the use of a multidimensional approach including the invasive measurement of cardiac index (CI)≥2.5l/min/m².

To avoid the use of right heart catheterization (RHC) and CI measurement in low risk PAH patients, we studied right ventricular systolic function in echocardiography (TTE) as surrogate for CI≥2.5l/min/m².

A total of 125 PAH patients (historic cohort) underwent 406 hemodynamic investigations (RHC and TTE on the same day). Tricuspid S wave tissue doppler velocity and TAPSE (tricuspid annular longitudinal excursion by M-mode) were performed in accordance with 2015 EACVI/ASE recommendations. This cohort served for the receiver operating characteristic analysis from which the cutoffs were applied to a validation cohort of 97 PAH patients, to identify those with CI≥2.5l/min/m².

From the historic cohort, both tricuspid S wave and TAPSE were correlated to invasive CI (P<0.001 and P<0.0001, respectively). From the ROC curve analysis, tricuspid S wave≥12cm/s had a specificity of 0.89 to detect CI≥2.5l/min/m² (area under the curve, AUC=0.74) while TAPSE >17mm had a specificity of 0.59 to detect CI≥2.5l/min/m² (AUC=0.69). TAPSE depicted greater interest when tricuspid S wave ranged between 10 and 12cm/s. Thus, from 97 PAH patients, 45 (46%) were appropriately classified by TTE as having CI≥2.5l/min/m² meaning that we could have avoided RHC in almost 50% of patients; 7 patients were misclassified and 45 were unclassified (Figure 1).

Considering tricuspid S wave tissue Doppler velocity≥12cm/s or<12cm/s but≥10cm/s with TAPSE>17mm, then RHC may be avoided in almost 50% of patient with<7% of false negative to predict CI≥2.5l/min/m² (low risk clinical worsening or death) in PAH patients.