title: Cardiac structure and function in adolescent Sherpa; effect of habitual altitude and developmental stage.
abstract: 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.
authors.affiliation: Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom; mstembridge@cardiffmet.ac.uk.
authors.forename: Mike
authors.initials: M
authors.lastname: Stembridge
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, Kelowna, British Columbia, Canada;
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
authors.affiliation: Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom;
authors.forename: Joseph
authors.initials: J
authors.lastname: Donnelly
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina;
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: MacLeod
authors.affiliation: Patan Academy of Health Sciences, Kathmandu, Nepal; and.
authors.forename: Suchita
authors.initials: S
authors.lastname: Joshi
authors.affiliation: Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom;
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hughes
authors.affiliation: Khunde Hospital, Khunde, Nepal.
authors.forename: Kami
authors.initials: K
authors.lastname: Sherpa
authors.affiliation: Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom;
authors.forename: Rob
authors.initials: R
authors.lastname: Shave
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000293:Adolescent; D041923:Adolescent Development; D000531:Altitude; D044466:Asian People; D016022:Case-Control Studies; D002648:Child; D015150:Echocardiography, Doppler; D006321:Heart / Q000254:growth & development*; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D000860:Hypoxia / Q000000981:diagnostic imaging*; D008297:Male; D009390:Nepal; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right; D044465:White People
keywords: diastolic function; high altitude; hypoxia; left ventricular mechanics; untwist velocity