Usefulness of NT-proBNP dosage during the follow-up of PAH: Comparison with 6MWD

INTRODUCTION: Pulmonary Arterial Hypertension (PAH) is a rare disease with poor prognosis that needs early diagnosis and aggressive therapy. 6-min walk distance (6MWD) has been diffusely used for clinical follow-up and therapy response. Serum NT-proBNP has been recently used to assess right ventricular dysfunction. PURPOSE: To analyze association between NT-proBNP and 6MWD and their distribution in different World Health Organization (WHO) functional class. METHODS: We followed 34 patients (pts) affected by group 1 PAH with a median follow-up of 31 months (m) (min. 1 – max 69 m) for a total of 431 visits. At each visit, all pts were clinically evaluated into WHO status and prospectively performed at same daily-time 6MWD, preceded by NT-proBNP dosage not more than 10 minutes before walking. RESULTS: Pearson correlation index between NT-proBNP and 6MWD resulted -0.60 (p 1400pg/mL, 93% of the 6MWT were ≤380m; only 56% of pts with NT-proBNP≤1400pg/mL walked >380m, probably due to physical confounding factors (age, sex weight, etc). During follow-up period, no pts in WHO I-II had NT-proBNP>1400pg/mL, while 15% of pts in WHO class I-II walked CONCLUSION: If performed together, NT-proBNP and 6MWT had an inverse correlation. These results may suggest low clinical utility of follow-up 6MWT in pts with NT-proBNP>1400pg/mL, highlighted by their compromised functional class (WHO III-IV). A cut-off of 380m at 6MWT was not able to define a correct WHO status, whereas NT-proBNP>1400pg/mL may exclude pts in WHO I-II.