The prevalence of congenital heart disease (CHD) in Tibet has not been fully investigated. The aim of this study was to illustrate and compare the prevalence of symptomatic CHD and its major subtypes in Tibetan children at different altitudes. A total of 5,790 children from regions at altitudes of 3,500 to 4,100 m (group L) and 4,548 children from 4,200 to 4,900 m (group H) were compared for CHD prevalence. Group H had greater prevalence of total CHD (12.09 vs 4.32 per 1,000, p <0.001), patent ductus arteriosus (PDA, 7.70 vs 1.38 per 1,000, p <0.001), and atrial septal defect (ASD, 3.52 vs 2.25 per 1,000, p = 0.23) than group L. The differences were more remarkable in women (CHD, 18.63 vs 4.88 per 1,000, p <0.001; PDA, 11.53 vs 1.74 per 1,000, p <0.001; ASD, 5.32 vs 2.79 per 1,000, p = 0.15). No significant difference was observed in the prevalence of ventricular septal defect between the 2 groups (0.44 vs 0.35 per 1,000, p >0.05). The most common cardiac defect was ASD (52.0%) in group L compared with PDA (63.6%) in group H. In group L, women had slightly and insignificantly greater prevalence of total CHD, PDA, and ASD than men. In contrast, the prevalence was almost threefold greater in women than men in group H. In conclusion, the CHD prevalence and composition differed significantly between populations of school children living above and below 4,200 m.
Tibetan Plateau is the highest region on earth, with an average elevation of 4,500 m. Living at high altitudes under hypoxic conditions has some potential effects on the heart. Some studies have described the prevalence of congenital heart disease (CHD) in certain parts of Tibet and suggested the low oxygen tension profoundly affected the CHD prevalence at high altitude. However, only a very small minority of the study population were from regions above 4,200 m, where a large number of Tibetans were living. We hypothesized that with increasing altitudes, the prevalence of CHD and its major subtypes might be different from that at lower altitudes. In this study, we aimed to illustrate and compare the prevalence of symptomatic CHD in Tibetan children at different altitudes and discuss the possible mechanisms.
Methods
CHD was defined as a gross structural abnormality of the heart or intrathoracic great vessels that are actually or potentially of functional significance. A patent foramen ovale or atrial septal defect (ASD) of <5 mm in diameter was not considered as a cardiac anomaly because of its high rate of spontaneous closure or regression in size with aging. Additionally, idiopathic pulmonary arterial hypertension with or without a small ASD was excluded from the spectrum of CHD.
From October 2012 to April 2013, we conducted a CHD screening study of unselected Tibetan children aged from 3 to 15 years in different regions of Tibet. We recruited a total of 5,790 children (men, 50.5% and women, 49.5%) from the eastern regions of Changdu (with altitudes ranging from 3,500 to 4,100 m, designated as group L) and 4,548 children (men, 50.4% and women, 49.6%) from the western regions of Shigatse (4,200 to 4,900 m, designated as group H). The children were from schools, kindergartens, and nearby villages. No children in the 2 regions had been examined or treated by cardiovascular specialists before the study.
We examined each child physically in quiet local school rooms. Children with abnormal signs suggestive of a possible cardiac defect, including exertional intolerance, growth retardation, cardiac murmurs, fixed splitting of S2, accentuated pulmonary component of S2, clinical cyanosis, clubbing of fingers, and weak femoral artery pulses, were candidates for echocardiography. Considering the influence of pulmonary hypertension, very mild cardiac murmurs were noted as an indication for echocardiography.
Echocardiography was performed using the Vivid i cardiovascular ultrasound system (GE Healthcare, Horten, Norway). Two-dimensional scanning with Doppler imaging was checked from parasternal, apical, subcostal, and suprasternal views. Pulmonary artery systolic pressure was estimated from the peak velocity of tricuspid regurgitation or the pressure gradient across ventricular septal defect (VSD) or patent ductus arteriosus (PDA). The study was carried out in accordance with the ethical principles in the Declaration of Helsinki, and informed consent was obtained from the parents or legal guardian of each child.
Statistical analysis was performed with SPSS version 15.0 (SPSS, Chicago, Illinois). The prevalence of CHD was expressed as number of cases per 1,000 and compared using the chi-square or Fisher’s exact test. A 2-sided p value <0.05 was considered statistically significant.
Results
Echocardiography was performed in 7.4% of the children in group L and 8.1% in group H. Twenty-five children in group L and 55 in group H were diagnosed to have CHD, with a greater prevalence in group H (4.32 vs 12.09 per 1,000, p <0.001).
Table 1 lists the prevalence of CHD and its major subtypes classified by the altitudes of residence. The most common cardiac defect was ASD (52.0%) in group L compared with PDA (63.6%) in group H. In group L, women had slightly and insignificantly greater prevalence of total CHD, PDA, and ASD than men. In contrast, the prevalence were almost threefold greater in women than men in group H.
| Defect | Group L | Group H | ||||
|---|---|---|---|---|---|---|
| Total (n = 5,790) | Men (n = 2,924) | Women (n = 2,866) | Total (n = 4,548) | Men (n = 2,293) | Women (n = 2,255) | |
| PDA | 8 (1.38) | 3 (1.03) | 5 (1.74) | 35 (7.70) | 9 (3.93) | 26 (11.53) |
| ASD | 13 (2.25) | 5 (1.71) | 8 (2.79) | 16 (3.52) | 4 (1.74) | 12 (5.32) |
| VSD | 2 (0.35) | 1 (0.34) | 1 (0.35) | 2 (0.44) | 0 | 2 (0.89) |
| PS | 1 (0.17) | 1 (0.34) | 0 | 0 | 0 | 0 |
| TOF | 1 (0.17) | 1 (0.34) | 0 | 0 | 0 | 0 |
| ASD PDA | 0 | 0 | 0 | 1 (0.22) | 0 | 1 (0.44) |
| VSD PDA | 0 | 0 | 0 | 1 (0.22) | 0 | 1 (0.44) |
| Total | 25 (4.32) | 11 (3.76) | 14 (4.88) | 55 (12.09) | 13 (5.67) | 42 (18.63) |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
