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/(AxS) (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 30.5years were assessed at baseline and at >150minutes following hypobaric hypoxia (HH) to the equivalent altitude of 4800m for a total of 180minutes. The combined EAS index (E/(AxS)) 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 +/- 0.7L/min vs. 6.1 +/- 1.2L/min; P<0.0001), peak pulmonary artery systolic pressure (PASP) (26.3 +/- 2.0mmHg vs. 37.2 +/- 6.3mmHg; 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 R2=0.77; P<0.0001). The right and LV EAS indices were significantly correlated (r=0.45; 95% CI: 0.070.7; 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. (Echocardiography 2013; 30: 534-541)