Anatomical and hemodynamic evaluations of the heart and pulmonary arterial pressure in healthy children residing at high altitude in China.

OBJECTIVES: Altitude-hypoxia induces pulmonary arterial hypertension and altered cardiac morphology and function, which is little known in healthy children at high altitude. We compared the cardiopulmonary measurements between the healthy children at 16 m and those at 3700 m in China and between the Hans and the Tibetans at 3700 m. METHODS: Echocardiography was assessed in 477 children (15 day-14 years) including 220 at 16 m and 257 at 3700 m. The dimensions and wall thickness of the left- and right-sided heart, systolic and diastolic functions including cardiac output index (CI) were measured using standard methods. Mean pulmonary arterial pressure (mPAP) was estimated by the Doppler waveforms in the main pulmonary artery. RESULTS: Compared to the 16 m-group, 3700 m-group had higher mPAP, increasing dilatation of the right heart, and slower decrease in right ventricular hypertrophy in 14 years (p < 0.05). The left heart morphology was not different (p > 0.20). Systolic and diastolic functions of both ventricles were significantly reduced, but CI was higher (p < 0.0001). There was no difference in any measurement between the Hans and the Tibetans (p > 0.05). CONCLUSIONS: Children living at high altitude in China have significantly higher mPAP, dilated right heart and slower regression of right ventricular hypertrophy in the first 14 years of life. Systolic and diastolic functions of both ventricles were reduced with a paradoxically higher CI. There was no significant difference in these features between the Hans and the Tibetans. These values provide references for the care of healthy children and the sick ones with cardiopulmonary diseases at high altitude.

Changes of cardiac structure and function in pediatric patients with high altitude pulmonary hypertension in Tibet.

This study was performed to evaluate the structural and functional cardiac changes in pediatric high altitude pulmonary hypertension (HAPH) using magnetic resonance imaging (MRI) and Doppler echocardiography (Echo). Ten patients with infantile HAPH (aged 12 to 24 months) and eight healthy age-matched children (control group) underwent MRI and Echo studies. All participants were born and living in the Qinghai-Tibetan Plateau (3600 to 4600 m). The studies were performed at the Children's Hospital located in Xining, Qinghai (2260 m). The right and left ventricular end-systolic (RVEST and LVEST, respectively) and end-diastolic (RVEDT and LVEDT, respectively) wall thicknesses were calculated directly from the MRI scans. The mean pulmonary arterial pressure (mPAP) was measured using Echo. RVEST was significantly higher in the HAPH group than in the control group (6.8 +/- 0.6 and 3.7 +/- 0.5 mm, respectively; p < 0.001). RVEDT was significantly higher in the HAPH patients when compared with the control group (4.9 +/- 1.1 and 2.1 +/- 0.3 mm, respectively; p < 0.05). Mean PAP in the HAPH group was significantly higher than in the control group (66.8 +/- 6.7 and 33.8 +/- 3.6 mmHg, respectively; p < 0.001) and was positively correlated with RVEDT (r(2) = 0.562, p < 0.001). Right ventricular ejection fraction was significantly lower in the HAPH group when compared with the control group (29.8 +/- 11.8 and 55.5 +/- 9.9%, respectively; p < 0.001); however, left ventricular ejection fraction was similar in both groups. These results indicate that hypoxia-induced infantile HAPH leads to right ventricular hypertrophy in these patients. These structural cardiac changes may lead to right ventricular dysfunction and right heart failure; however, left ventricular function is preserved.

[Comparitive [Comparative] study of the indexes of pulmonary arterial pressure of healthy children at different altitudes by Doppler echocardiography].

OBJECTIVE: Reduced oxygen availability at a high altitude is associated with increased pulmonary arterial pressure (PAP). With the altitude goes up the change of PAP in healthy children is still not clear. The difference of PAP in native Tibetan and Han children at a high altitude are also not clear. Many studies have shown that Doppler echocardiographic estimation of PAP correlates closely to the values obtained with the invasive measurement. Therefore the indexes of PAP in health children living at different altitudes were investigated and the indexes of PAP in Han and Tibetan children at the high altitude were compared by Doppler echocardiography. METHODS: A randomized survey was carried out on the indexes of PAP with Doppler echocardiography (HP-8500 and CAL-163 echocardiographic machine) by two doctors of Qinghai Provincial Women and Children Hospital from June 1998 to July 2002. The survey covering Jiuzhi Qinghai (at 3700 m above the sea level), Xining Qinghai (at 2260 m above the sea level) and Shanghai (at 16 m above the sea level) included a population of 1061 children aged 0 - 14 years. The population of 1061 composed of 218 Han children at Shanghai, 567 Han children at Xining Qinghai and 276 children at Jiuzhi, Qinghai including 118 migrated Han and 148 native Tibetan children. The physical, EKG and chest X-ray examination of each child were carried out to ensure all the subjects were healthy. A pulse oximeter was placed on each child's foot to provide measurements of arterial oxygen saturation (SO2) distal to the ductus arteriosus. The indexes of PAP included right ventricular systolic time interval (RSTI) and mean of pulmonary arterial pressure (mPAP) which was assessed by a multiple regression equation (mPAP=27.79 + 35.42 x PEP/AT-50.85 x AT/ETc). The AT/ETc was that AT/ET was divided by R-R. The RSTI included previous ejection period (PEP), ascending time (AT), ejection time (ET), PEP/AT and AT/ET. All subjects were divided into 7 age groups. The data of PAP indexes were compared among three different altitude groups and age groups. The data of PAP indexes were also compared in Han and Tibetan children living over 3700 m sea level in each age group. RESULTS: With the altitude increase the SO2 of the subjects obviously reduced and the indexes of PAP changed. The SO2 correlated closely with the PEP, AT, PEP/A, AT/ET and mPAP (r = 0.352, 0.144, -0.394, -0.166 and -0.363, respectively; P < 0.01). The AT and AT/ET in the groups of 2260 m and 3700 m were shorter than those in the group of 16 m (P = 0.03-0.000) in each age group. The PEP and PEP/AT in 3700 m group were longer than those in 2260 m and 16 m groups (P=0.006-0.000) in each age group. The mPAP in 3700 m group was higher than that in 2260 m and 16 m groups in each age group (mean [+/-SE] mmHg, 35.23 +/- 8.72 vs 17.99 +/- 8.78 and 15.86 +/- 8.96 aged 0 - 28 d, 32.06 +/- 13.38 vs 20.72 +/- 5.71 and 14.64 +/- 8.19 aged to 6 mo, 31.83 +/- 10.53 vs 20.89 +/- 10.12 and 14.69 +/- 5.89 aged to 1 yr, 27.58 +/- 13.55 vs 19.12 +/- 9.75 and 17.36 +/- 6.71 aged to 3 yr, 24.19 +/- 8.38 vs 19.64 +/- 9.36 and 16.43 +/- 4.68 aged to 6 yr, 23.90 +/- 11.35 vs 16.77 +/- 6.79 and 14.42 +/- 6.50 aged to 10 yr, 23.08 +/- 7.31 vs 18.53 +/- 7.25 and 15.45 +/- 6.12 aged to 14 yr, P=0.000). With the growth of the children the reduction of PAP was remarkable at 3700 m above sea level (F=5.638 P=0.000), the mPAP indexes of the first, second and third age groups were evidently higher than those of the other age groups. The SO2, RSTI and mPAP in the native Tibetan children were not different from those in the migrated Han children (P > 0.05) in each age group. CONCLUSION: The PAP of healthy children at the high altitude was different from that of healthy children at the low altitude. The PAP of the healthy children at 3700 m above sea level was remarkably increased. At 3700 m above sea level the PAP of newborns and infants increased much more compared with that of juvenile. The race may not significantly affect the PAP at the high altitude. The high altitude hypoxic environment might play a major role in the increase of PAP.