Cardiac structure and function in adolescent Sherpa; effect of habitual altitude and developmental stage
MacLeod, Nicholas T.
Hughes, Michael G.
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The purpose of this study was to examine ventricular structure and function in Sherpa adolescents to determine whether age-specific differences in oxygen saturation (SpO2) and pulmonary artery systolic pressure (PASP) influence cardiac adaptation to chronic hypoxia early in life. Two-dimensional, Doppler, and speckle-tracking echocardiography were performed on adolescent (9–16 yr) highland Sherpa (HLS; 3,840 m; n = 26) and compared with age-matched lowland Sherpa (LLS; 1,400 m; n = 10) and lowland Caucasian controls (LLC; sea level; n = 30). The HLS were subdivided into pre- and postadolescence; SpO2 was also recorded. Only HLS exhibited a smaller relative left ventricular (LV) end-diastolic volume; however, both HLS and LLS demonstrated a lower peak LV untwisting velocity compared with LLC (92 ± 26 and 100 ± 45 vs. 130 ± 43°/s, P < 0.05). Although SpO2 was similar between groups, PASP was higher in post- vs. preadolescent HLS (30 ± 5 vs. 25 ± 5 mmHg, P < 0.05), which negatively correlated with right ventricular strain rate (r = 0.50, P < 0.01). Much like their adult counterparts, HLS and LLS adolescents exhibit slower LV diastolic relaxation, despite residing at different altitudes. These findings suggest fundamental differences exist in the diastolic function of Sherpa that are present at an early age and may be retained after migration to lower altitudes. The higher PASP in postadolescent Sherpa is in contrast to previous reports of lowland children at high altitude and, unlike that in lowlanders, was not explained by differences in SpO2; thus different regulatory mechanisms seem to exist between these two distinct populations.
American Journal of Physiology: Heart and Circulatory Physiology;
Stembridge, M., Ainslie, P., Donnelly, J., MacLeod, N.T., Joshi, S., Hughes, M.G., Sherpa, K and Shave, R. (2016) 'Cardiac structure and function in adolescent Sherpa; effect of habitual altitude and developmental stage', American Journal of Physiology: Heart and Circulatory Physiology, 310(6), pp.740-746
This article was published in American Journal of Physiology: Heart and Circulatory Physiology on 15 March 2016 (online), available at http://dx.doi.org/10.1152/ajpheart.00938.2015
This study was carried out within the framework of the Ev-K2-CNR Project in collaboration with the Nepal Academy of Science and Technology as foreseen by the Memorandum of Understanding between Nepal and Italy, and thanks to contributions from the Italian National Research Council. This study was supported in part by the Natural Sciences and Engineering Research Council of Canada and a Canada Research Chair to PNA. The authors are grateful to the other members of this international research expedition for assistance with the organization of this project.
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