Comparison of Echocardiographic Parameters Between Healthy Highlanders in Tibet and Lowlanders in Beijing.

Yang, Ying, Duo-Ji Zha-Xi, Wei Mao, Guang Zhi, Bin Feng, and Yun-Dai Chen. Comparison of echocardiographic parameters between healthy highlanders in Tibet and lowlanders in Beijing. High Alt Med Biol. 19:259-264, 2018.-The hearts of highlanders exhibit distinct features compared with the hearts of lowlanders. However, previous findings have not been verified in a large-scale Tibetan population study. The aim of this study was to present differences in echocardiography results among healthy native Tibetans, acclimatized Han highlanders, and Han lowlanders at sea level. A total of 1820 healthy Tibetans and 224 healthy Han highlanders were drawn from a representative sample of residents in Tibet. Echocardiography was performed on each participant at the sampled local medical centers. Echocardiographic data from 2332 healthy Han lowlanders were obtained from a database of a medical examination center in Beijing. Using propensity score matching to balance differences in demographic features, we evaluated the effects of altitude and ethnicity in three paired comparisons. The results revealed that the great arteries were larger in the Han population than in the Tibetan population regardless of altitude (all p < 0.05). No differences were found in the right atrium between different altitudes and ethnicities. The diameters and thicknesses of the right ventricle (RV) were larger in the Tibetans than in the Han lowlanders (i.e., 30.0 mm (26.0, 34.0) versus 28.6 mm (25.5, 31.8) for the basal right ventricular linear dimension). The left heart in diastole was largest in the Han lowlanders (i.e., 46.3 ± 3.9 mm versus 43.0 mm [40.0, 44.0] in Han highlanders and 45.8 mm [43.0, 48.8] versus 42.0 mm [39.0, 45.0] in Tibetans for the diameter of the left ventricle [LV] at end-diastole). Moreover, the interventricular septum was thicker in the high-altitude population than in the low-altitude population (all p < 0.05). Compared with the Tibetans, the Han highlanders exhibited enhanced ventricular functions (65.0% [60.0, 69.0] versus 68.0% [63.0, 69.0] for LV ejection fraction and 22.0 mm [20.0, 26.0] versus 24.0 mm [21.0, 27.0] for tricuspid annular plane systolic excursion, both p < 0.05). In conclusion, a small left heart and a large RV may be consequences of hypoxic exposure at high altitudes irrespective of ethnic origin.