Prevalence and composition of CHD at different altitudes in Tibet: a cross-sectional study

BACKGROUND: The prevalence of CHD has been well described worldwide except in Tibet. This study aimed to illustrate the prevalence and composition of CHD in Tibetan children according to altitude. Methods and results In the first part, we prospectively recruited 7088 unselected Tibetan children (4-17 years) from south-west Tibet. The total prevalence of CHD increased from 4.6/1000 below 4200 m to 13.4/1000 above 4700 m, with a female-to-male ratio of 1.3:3.1. The total prevalence and female prevalence of patent ductus arteriosus increased more than 10-fold. Females living above 4700 m had exceptionally high prevalence of patent ductus arteriosus (14.9/1000). The prevalence of atrial septal defect was comparable among different altitudes (3.3-3.8/1000). The prevalence of ventricular septal defect was 1.3/1000 below 4700 m, and no cases were found above this altitude. In the second part, we retrospectively reviewed the clinical data of 383 CHD children in Tibet and 73 children at lower altitudes. The percentage of isolated ventricular septal defect decreased from 54.8 to 3.1%, and the percentage of isolated patent ductus arteriosus increased from 8.2 to 68.4% with elevation. Children living below 4200 m (10.4-13.7%) had a larger proportion of complex CHD than those above this altitude (2.0-3.1%). Of the 20 Tibetan children with complex CHD, 14 (70.0%) lived below 4200 m. CONCLUSIONS: A wide variation in CHD prevalence and composition existed in Tibetan children among different altitudes.