Surviving birth at high altitude

This Symposium Review examines challenges to surviving birth and infancy at high altitudes. Chronic exposure to the environmental hypoxia of high altitudes increases the incidence of maternal vascular disorders of pregnancy characterized by placental insufficiency, restricted fetal growth and preterm delivery, and impairs pulmonary vascular health during infancy. While each condition independently contributes to excess morbidity and mortality in early life, evidence indicates vascular disorders of pregnancy and infantile pulmonary vascular dysfunction are intertwined. By integrating our recent scientific and clinical observations in Bolivia with existing literature, we propose potential avenues to reduce the infant mortality burden at high altitudes and reduce pulmonary vascular disease in highland neonates, and emphasize the need for further research to address unresolved questions.

Vascular Disorders of Pregnancy Increase Susceptibility to Neonatal Pulmonary Hypertension in High-Altitude Populations

BACKGROUND

Preeclampsia and fetal growth restriction increase cardiopulmonary disease risk for affected offspring and occur more frequently at high-altitude (≥2500 m). Retrospective studies indicate that birth to a preeclampsia woman at high altitude increases the risk of pulmonary hypertension (PH) in later life. This prospective study asked whether preeclampsia with or without fetal growth restriction exaggerated fetal hypoxia and impaired angiogenesis in the fetal lung, leading to neonatal cardiopulmonary circulation abnormalities and neonatal or infantile PH.

METHODS AND RESULTS

We studied 79 maternal-infant pairs (39 preeclampsia, 40 controls) in Bolivia (3600-4100 m). Cord blood erythropoietin, hemoglobin, and umbilical artery and venous blood gases were measured as indices of fetal hypoxia. Maternal and cord plasma levels of angiogenic (VEGF [vascular endothelial growth factor]) and antiangiogenic (sFlt1 [soluble fms-like tyrosine kinase]) factors were determined. Postnatal echocardiography (1 week and 6-9 months) assessed pulmonary hemodynamics and PH. Preeclampsia augmented fetal hypoxia and increased the risk of PH in the neonate but not later in infancy. Pulmonary abnormalities were confined to preeclampsia cases with fetal growth restriction. Maternal and fetal plasma sFlt1 levels were higher in preeclampsia than controls and positively associated with PH.

CONCLUSIONS

The effect of preeclampsia with fetal growth restriction to increase fetal hypoxia and sFlt1 levels may impede normal development of the pulmonary circulation at high altitude, leading to adverse neonatal pulmonary vascular outcomes. Our observations highlight important temporal windows for the prevention of pulmonary vascular disease among babies born to highland residents or those with exaggerated hypoxia in utero or newborn life.

Developing High Medical Technology, a Challenge for Developing Countries: The Percutaneous Closure of Atrial Septal Defects Using Nit-Occlud ASD-R: Early and Mid-term Results

Objective:

To assess the efficacy and safety of the Nit-Occlud ASD-R (PFM S.R.L, La Paz, Bolivia) in the percutaneous closure of secundum atrial septal defects (ASD).

Patients and Methods:

Fifty-three consecutive patients with median age of 11 years (range 3-67) and mean weight 27.1 kg (range 13-75 kg), treated in two cardiology centers between May 2007 and March 2011.

Results:

Mean fluoroscopy time was 14 minutes (5-53), mean procedure time was 70 minutes (45-150), mean defect size, as measured by the stop-flow technique, was 17.8 mm (5.6-31), and mean stent size of the implanted device was 18 mm (6-28), which is 0.98 times the defect size. Successful closure of the ASD without major complications was achieved in 49 of 53 patients. In 71.4% of patients in whom device implantation was accomplished, there was no evidence of a persistent shunt at the completion of the procedure. This closure rate increased to 91.7% after 24 hours, with 95.8% closure after three months and 100% closure after six months. Device embolization occurred in one patient within 24 hours of implantation and required surgical device removal and ASD closure. There were no other major complications and no deaths during the period of follow-up (average 72 months; range 59-105 months).

Conclusion:

The Nit-Occlud ASD-R device is safe and effective with very good closure rates.