Pasp and Bnp/nt-­‐probnp Brain Natriuretic Peptide and Nt-probnp Levels Reflect Pulmonary Artery Systolic Pressure in Trekkers at High Altitude. Running Title: Pasp and Bnp/nt-probnp

11 12 13 14 15 16 17 18 19 PASP and BNP/NT-­‐proBNP 2 2 Summary 1 Our objective was to evaluate the utility of the natriuretic peptides BNP (brain natriuretic 2 peptide) and NT-proBNP as markers of pulmonary artery systolic pressure (PASP) in trekkers 3 ascending to high altitude (HA). 20 participants had BNP and NT-proBNP assayed and 4 simultaneous echocardiographic assessment of PASP performed during a trek to 5150 m. PASP 5 increased significantly (p=0.006) with ascent from 24±4 to 39±11 mm Hg at 5150 m. At 5150 m 6 those with a PASP ≥40 mm Hg (n=8) (versus those with PASP <40 mm Hg) had higher post-7 exercise BNP (pg/ml): 54.5±36 vs 13.4±17 (p=0.012). Their resting BNP at 5150 m was also 8 higher: 57.3±43.4 vs 12.6±13 (p=0.017). In those with a pathological (≥400 pg/ml) rise in NT-9 proBNP at 5150 m (n=4) PASP was significantly higher: 45.9±7.5 vs 32.2±6.2 mm Hg 10 (p=0.015). BNP and NT-proBNP may reflect elevated PASP, a central feature of high altitude 11 pulmonary oedema, at HA.