Abstract
OBJECTIVE: Pulmonary arterioles respond to hypoxia with constriction that raises vascular resistance and pulmonary artery blood pressure. The response is sustained indefinitely by the chronic hypoxia of high-altitude residence among highlanders of European and Andean descent, but not Tibetans. The objective of this study was to identify the consequences of lifelong hypoxia exposure for the pulmonary vasculature among Amhara high-altitude natives from Ethiopia. METHODS: A three-way static group comparison tested for the effect of Amhara ancestry and high residence altitude on pulmonary hemodynamics measured using echocardiography in samples of 76 healthy adult Amhara lifelong residents at 3700 m, 54 Amhara lifelong residents at 1200 m, and 46 U.S. low-altitude residents at 282 m. RESULTS: Amhara at 3700 m had average Doppler-estimated pulmonary artery systolic pressure (tricuspid regurgitant gradient) of 27.9 ± 8.4 (SD) mm Hg as compared with 21.9 ± 4.0 among Amhara at low altitude and 16.5 ± 3.6 in the U.S. low-altitude reference sample. However, there was no residence altitude effect on pulmonary blood flow or vascular resistance. Amhara ancestry was associated with greater pulmonary artery systolic pressure and pulmonary blood flow, yet lower pulmonary vascular resistance. CONCLUSIONS: The Amhara at 3700 m had elevated pulmonary artery pressure, but without the elevated pulmonary vascular resistance characteristic of the classic model of the response to long-term hypoxia by the pulmonary vasculature. The elevated pressure among Amhara may be a consequence of high pulmonary blood flow regardless of altitude and represent a newly identified pattern of response.