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Background: This study aimed to illustrate the prevalence of CHD by screening children in extremely high-altitude areas (over 4000 m to even 5000 m above sea level) and explore an aid model for early diagnosis and treatment for the Tibetan population. Methods: A total of 2242 students from different schools in Ngamring County, Xigaze City, Tibet from September 2019 to September 2020 were selected for screening. The students were examined through the inquiry of their current medical history and family history, cardiac auscultation and a physical examination, in order to screen out the suspected cases of CHD, and then the suspected cases were confirmed by cardiac color ultrasound examinations. After that, positive patients were be transferred to Shandong Province for free treatment. Results: The prevalence of CHD among children in Ngamring County was 3.70% (83 cases), which is the highest incidence rate ever reported. The most common type of CHD was patent ductus arteriosus (PDA), accounting for 55.42% of the total number of cases screened, followed by atrial septal defect (ASD) and ventricular septal defect (VSD), accounting for 28.92% and 12.05%, respectively. The prevalence of CHD in children at high altitude was significantly higher than that in children at low altitude. The children with CHD were transferred to Shandong Province for surgery, the operations were successful and their recoveries went well. Conclusions: The results show that high altitude is closely related to the prevalence of CHD, and the incidence in Ngamring County is much higher than that in previous reports. [ABSTRACT FROM AUTHOR]

Large-scale N-S shortening induced by India-Asia convergence caused the formation of numerous E-W--trending mountain ranges in Tibet. However, the mechanism(s) of formation of N-S--trending mountain ranges remains elusive. We report on a felsic magmatic belt located along the N-S--trending Yardoi-Kongbugang mountain ranges on the flank of the Cona rift in the eastern Tethyan Himalaya. Zircon and monazite geochronology and whole-rock geochemistry revealed three epochs of middle- to lower-crustal anatexis beneath the Cona rift at ca. 47-42 Ma, 35-34 Ma, and 24-14 Ma. The mid-Eocene and early Oligocene granitoids show adakitic signatures indicating continuous crustal thickening, while the formation of Miocene leucogranites and N-S--trending dacitic dikes was related to ductile crustal extension. Silicic melts were exposed along the whole rift since the early Oligocene, suggesting that the early Oligocene could be regarded as a transitional epoch from tectonic compression to orogen-parallel extension. Widespread mid-Eocene and Miocene magmatism in the Himalaya, together with coeval metamorphic anatexis, represents two phases of crustal weakening. The weakened crustal zones under continued India-Asia convergence may have favored uplift and subsequent lateral flow of the weak zones, which initiated E-W extension. Finally, significant upwelling of the weak zones evolved into magma extrusion and formed the N-S--trending mountain ranges. This study provides new insights into the mechanisms of surface uplift and E-W extension and challenges the common view of initiation of E-W extension in southern Tibet not earlier than the early Miocene. [ABSTRACT FROM AUTHOR]