Correlation Between N-Terminal Pro-Brain Natriuretic Peptide Levels and Cardiopulmonary Exercise Testing in Patients With Pre-Capillary Pulmonary Hypertension: A Pilot Study.

Background: N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiopulmonary exercise testing (CPET) are useful for severity assessment in patients with pulmonary hypertension (PH). Correlations between these tests in pre-capillary PH patients is less well studied.

Methods: We studied 23 patients with pre-capillary PH: 8 with idiopathic pulmonary arterial hypertension (IPAH), 6 with systemic sclerosis-associated PAH (SSc-PAH), and 9 with chronic thromboembolic pulmonary hypertension (CTEPH). Clinical evaluation, NT-proBNP levels, six-minute walking test (6MWT), spirometry, and CPET were evaluated on the same day. Correlation between NT-proBNP levels and CPET parameters were investigated.

Results: In all patients, NT-proBNP levels were significantly correlated with peak oxygen uptake (VO₂) (r = -0.47), peak oxygen pulse (r = -0.43), peak cardiac output (CO) (r = -0.57), peak end-tidal partial pressure of carbon dioxide (P_ETCO₂) (r = -0.74), ventilatory equivalent to carbon dioxide (VE/VCO₂) at anaerobic threshold (AT) (r = 0.73), and VE/VCO₂ slope (r = 0.64). Significant correlations between NT-proBNP levels and peak P_ETCO₂ and VE/VCO₂ were found in IPAH and CTEPH subgroups, and a significant correlation between NT-proBNP levels and VO₂ at AT was found in the CTEPH subgroup. No significant correlation was found in the SSc-PAH subgroup.

Conclusion: NT-proBNP levels were significantly correlated with CPET parameters in patients with IPAH and CTEPH subgroups, but not in SSc-PAH subgroup. A further study with larger population is required to confirm these preliminary findings.