Cardiac response to hypobaric hypoxia: persistent changes in cardiac mass, function, and energy metabolism after a trek to Mt. Everest Base Camp

Abstract

ABSTRACT We postulated that changes in cardiac high‐energy phosphate metabolism may underlie the myocardial dysfunction caused by hypobaric hypoxia. Healthy volunteers ( n =14) were studied immediately before, and within 4 d of return from, a 17‐d trek to Mt. Everest Base Camp (5300 m). 31 P magnetic resonance (MR) spectroscopy was used to measure cardiac phosphocreatine (PCr)/ATP, and MR imaging and echocardiography were used to assess cardiac volumes, mass, and function. Immediately after returning from Mt. Everest, total body weight had fallen by 3% ( P <0.05), but left ventricular mass, adjusted for changes in body surface area, had disproportionately decreased by 11% ( P <0.05). Alterations in diastolic function were also observed, with a reduction in peak left ventricular filling rates and mitral inflow E/A, by 17% ( P <0.05) and 24% ( P <0.01), respectively, with no change in hydration status. Compared with pretrek, cardiac PCr/ATP ratio had decreased by 18% ( P <0.01). Whether the abnormalities were even greater at altitude is unknown, but all had returned to pretrek levels after 6 mo. The alterations in cardiac morphology, function, and energetics are similar to findings in patients with chronic hypoxia. Thus, a decrease in cardiac PCr/ATP may be a universal response to periods of sustained low oxygen availability, underlying hypoxia‐induced cardiac dysfunction in healthy human heart and in patients with cardiopulmonary diseases.—Holloway, C. J., Montgomery, H. U., Murray, A. J., Cochlin, L. E., Codreanu, I. Hopwood, N., Johnson, A. W., Rider, O. J., Levett, D. Z. H., Tyler, D. J., Francis, J. M., Neubauer, S., Grocott, M. P. W., Clarke, K., for the Caudwell Xtreme Everest Research Group. Cardiac response to hypobaric hypoxia: persistent changes in cardiac mass, function, and energy metabolism after a trek to Mt. Everest Base Camp. FASEB J. 25, 792–796 (2011). www.fasebj.org