The Effects of Prolonged Acute Hypobaric Hypoxia on Novel Measures of Biventricular Performance

BACKGROUND: There are limited data on the effects of prolonged acute hypoxia on individual and global measures of biventricular function. AIMS: The aim of this study was to assess its effects on conventional and novel measures of biventricular function, including the recently defined E'/(A'×S') (EAS) index, obtained using pulsed-wave tissue Doppler Imaging (PWTDI) and associated blood brain natriuretic peptide (BNP) levels. METHODS: In this study, 14 healthy subjects aged 30.5 years were assessed at baseline and at >150 minutes following hypobaric hypoxia (HH) to the equivalent altitude of 4800 m for a total of 180 minutes. The combined EAS index (E'/(A' × S')) was calculated at the mitral and tricuspid annulus using data from the peak systolic (S') early (E') and late (A') diastolic filling. RESULTS: It was seen that HH increased resting heart rate (63.4 ± 8.4 vs. 85.2 ± 10.2/min; P < 0.0001), cardiac output (4.6 ± 0.7 L/min vs. 6.1 ± 1.2 L/min; P < 0.0001), peak pulmonary artery systolic pressure (PASP) (26.3 ± 2.0 mmHg vs. 37.2 ± 6.3 mmHg; P < 0.0001), and reduced SpO2 (98.5 ± 1.1 vs. 72.9 ± 8.1%; P < 0.0001). There was a significant reduction in mitral (0.19 ± 0.06 vs. 0.11 ± 0.03; P < 0.0001) and tricuspid (0.12 ± 0.04 vs. 0.09 ± 0.03; P = 0.03) EAS indices, but no change in left or right ventricular myocardial performance (Tei) indices, global left ventricular (LV) longitudinal systolic strain, BNP levels, or estimated filling pressures (E/E'). Only reducing SpO2 remained as an independent predictor of PASP on multivariate analysis (overall R(2) = 0.77; P < 0.0001). The right and LV EAS indices were significantly correlated (r = 0.45; 95% CI: 0.07-0.7; P = 0.02). CONCLUSION: The conclusion from this study was that acute prolonged HH does not adversely affect resting global biventricular function and there is evidence of linked right and LV responses.