High altitude-induced borderline pulmonary hypertension impaired cardiorespiratory fitness in healthy young men.

Objective: High altitude exposure has been suggested to cause borderline elevation of pulmonary artery pressure (PAP) in quite a few healthy individuals. This cohort study was to investigate the impact of altitude induced borderline pulmonary hypertension (PH) on cardiorespiratory fitness in healthy subjects.

Methods: 299 healthy Chinese young men with normal PAP were consecutively studied between July 2011 and September 2013. Among these subjects 114 kept living at low altitude (450m), 91 ascended to high altitude (3700m) from low altitude within 24h (acute exposure), and 94 resided at 3700m for more than 1year (chronic exposure). Mean PAP and cardiac function were examined by echocardiography, and cardiorespiratory fitness was determined by predicted work capacity at a heart rate of 170beats per minute (PWC170).

Results: Mean PAP remained within normal range (<20mmHg) in 113 of 114 participants (99%) at low altitude. In contrast, the incidence of borderline PH (mPAP between 20 and 25mmHg) was 29% and 37% for respective acute and chronic exposures. Compared to the subjects with normal mPAP within each of the exposure groups, the subjects with borderline PH had increased right ventricular Tei index (RV-Tei), which correlated with the decline of PWC170 (acute exposure: r=-0.296, p=0.004; chronic exposure: r=-0.247, p=0.016). However, these changes were relatively milder than those with confirmed PH (mPAP>25mmHg).

Conclusion: Borderline PH compromised cardiorespiratory fitness in healthy young men. The decline of cardiorespiratory fitness was related at least in part with the impaired right ventricular function, which was correlated with the elevated mPAP.