N-terminal pro-brain natriuretic peptide (NT-proBNP) is a marker of neurohormonal activation that is useful in the diagnosis and prognosis of various forms of pulmonary arterial hypertension (PAH). We sought to characterise and compare NT-proBNP in a cohort of PAH related to systemic sclerosis (PAH-SSc) and idiopathic PAH (IPAH) patients.NT-proBNP levels, collected from PAH-SSc and IPAH patients followed prospectively, were compared and correlated with haemodynamic variables. Cox proportional hazard models were created to assess the predictive value of NT-proBNP.98 patients (55 PAH-SSc, 43 IPAH) were included. Haemodynamics were similar, except for lower mean pulmonary arterial pressure in PAH-SSc. NT-proBNP levels were significantly higher in PAH-SSc (3,419¡3,784 versus 1,393¡1,633 pg?mL -1 ; p,0.01) and were more closely related to haemodynamics in PAH-SSc than IPAH. 28 patients died. NT-proBNP predicted survival (hazard ratio (HR) 3.18; p,0.01) in the overall cohort; however, when stratified by group, predicted survival only in PAH-SSc (HR 3.07, p,0.01 versus 2.02, p50.29 in IPAH). This is the first description showing NT-proBNP levels are 1) significantly higher in PAH-SSc than IPAH despite less severe haemodynamic perturbations, and 2) stronger predictors of survival in PAH-SSc, suggesting that neurohormonal regulation may differ between PAH-SSc and IPAH. Future studies to define pertinent mechanisms are warranted.

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RationalePulmonary arterial hypertension (PAH) is characterized by an increase in pulmonary vascular resistance leading to right ventricular (RV) failure and death. RV function is a major determinant of outcomes in this disease. N-terminal pro-brain natriuretic peptide (NT-proBNP) is a serum marker of RV dysfunction that is predictive of survival in PAH. We sought to evaluate the relationship between NT-pro-BNP and RV function as assessed by cardiac MRI (CMRI), echocardiography, and right heart catheterization (RHC) in patients with PAH. MethodsWe prospectively enrolled 49 patients who underwent echocardiography, RHC, and CMRI within 24 hours. Patients had an NT pro-BNP level drawn within 1 week of RHC. Invasive and non-invasive measures of RV function were compared to serum NT-proBNP levels using Mann-Whitney, Spearman's rank correlation and chi-square tests. ResultsA total of 49 patients with PAH were enrolled. Overall patients tended to be Caucasian women (82 and 88%, respectively) in functional class II or III (86 %). The mean 6MWD was 366.42 +/-116.78. The mean NT-proBNP was 2,870+/-5,405 pg/mL. The majority of the patients had moderately severe PAH (mean RAP: 8 +/-4 mmHg; mean PAP: 41 +/-13 mmHg, mean CI: 2.6 +/-0.8 L/min/m2; mean PVR: 7.7 +/-5.4 Wood units). NT-proBNP had strong correlations with measures of RV systolic function, such as CO (r=-0.60, p<0.001) and SVI (r=-0.51, p<0.001); right heart remodeling, such as right ventricular area index (r=0.79, p<0.01) and VMI (r=0.637, p=0.001); and RV afterload, such as SV/PP (r=-0.688, p<0.001 and PVR (r=0.61, p<0.001), but only a modest association with TAPSE, a measure of global RV function (r=-0.482, p:0.003). Interestingly, NT-proBNP correlated strongly with CMRI measurements of LV function: LVEDV (r=-0.70, p<0.001) and LV diameter (r=-0.70, p<0.01). Conclusions NT-proBNP is strongly correlated with various hemodynamic, echocardiographic, and MRI parameters reflecting RV function in PAH. Interestingly, we also found a strong relationship between CMRI measures of LV size and function. Further studies are needed to examine the components of RV function in PAH that are most closely reflected by NT-proBNP and to assess the relationship between LV function and NT-proBNP in these patients. Table 1. Hemodynamics Function Parameters Mean value RV systolic function CI (L/min/m) 2.6 (0.8) SVI (mL/m) 35.0 (0.01) PA saturation (%) 68.3 (7.9) RVSWI (g/m/beat) 15.5 (6.1) RVFAC (%) 33 (12) RVSV (ml) 58 (19) RVEF (%) 40 (14) Right heart remodeling RAA index (cm/m) 12.5 (4.6) RVA index (cm/m) 14.9 (3.2) RV mass index (g/cm) 36.7 (16.7) RV diameter (cm) 4.3 (0.9)