Left ventricular function during acute high-altitude exposure in a large group of healthy young Chinese men.

Mingyue Rao,Guozhu Chen,Jun Jin,Jihang Zhang,Rongsheng Rao,Jie Yu,Shiyong Yu,Huijie Li,Baida Xu,Jun Qin,Lan Huang,Jiabei Li,Xubin Gao,Renate B Schnabel

doi:10.1371/journal.pone.0116936

Mingyue Rao, Guozhu Chen + Show 12 more

Open Access

https://doi.org/10.1371/journal.pone.0116936

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Journal: PloS one	Publication Date: Jan 28, 2015
Citations: 24	License type: CC BY 4.0

Affiliation: Army Medical University, Xinqiao Hospital

Abstract

ObjectiveThe purpose of this study was to observe left ventricular function during acute high-altitude exposure in a large group of healthy young males.MethodsA prospective trial was conducted in Szechwan and Tibet from June to August, 2012. By Doppler echocardiography, left ventricular function was examined in 139 healthy young Chinese men at sea level; within 24 hours after arrival in Lhasa, Tibet, at 3700 m; and on day 7 following an ascent to Yangbajing at 4400 m after 7 days of acclimatization at 3700 m. The resting oxygen saturation (SaO2), heart rate (HR) and blood pressure (BP) were also measured at the above mentioned three time points.ResultsWithin 24 hours of arrival at 3700 m, the HR, ejection fraction (EF), fractional shortening (FS), stroke volume (SV), cardiac output (CO), and left ventricular (LV) Tei index were significantly increased, but the LV end-systolic dimension (ESD), end-systolic volume (ESV), SaO2, E/A ratio, and ejection time (ET) were significantly decreased compared to the baseline levels in all subjects. On day 7 at 4400 m, the SV and CO were significantly decreased; the EF and FS Tei were not decreased compared with the values at 3700 m; the HR was further elevated; and the SaO2, ESV, ESD, and ET were further reduced. Additionally, the E/A ratio was significantly increased on day 7 but was still lower than it was at low altitude.ConclusionUpon acute high-altitude exposure, left ventricular systolic function was elevated with increased stroke volume, but diastolic function was decreased in healthy young males. With higher altitude exposure and prolonged acclimatization, the left ventricular systolic function was preserved with reduced stroke volume and improved diastolic function.

Highlights

In recent years, increasing numbers of individuals have been exposed to high-altitude environments through entertainment, physical training, work, or habitation
On day 7 at 4400 m, the stroke volume (SV) and cardiac output (CO) were significantly decreased; the ejection fraction (EF) and fractional shortening (FS) Tei were not decreased compared with the values at 3700 m; the heart rate (HR) was further elevated; and the SaO2, end-systolic volume (ESV), end-systolic dimension (ESD), and ejection time (ET) were further reduced
This is in keeping with previous findings that suggested that left ventricular (LV) systolic function was improved in hypoxic healthy volunteers [1,2,3,22,23] and even in studies referring to adults and children exposed to high altitude [21,24]

Summary

Introduction

In recent years, increasing numbers of individuals have been exposed to high-altitude environments through entertainment, physical training, work, or habitation. Exposure to hypobaric hypoxia is associated with a series of adaptive responses, such as cardiovascular compensation, to combat the diminished arterial oxygen content. The initial cardiac response to hypoxia is characterized by an increase in cardiac output with tachycardia [1,2,3], which helps maintain oxygen delivery. Accurate delineation of the cardiovascular alterations after subjects have been at high altitudes has interested investigators since the early years of the last century [4,5]. Previous reports show stroke volume adaptations ranging from a decrease to a distinct increase [6,8,9,10]

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