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HIGH ALTITUDE AND CONGENITAL HEART DISEASE IN ANDEAN HIGHLANDS POPULATIONS: THE CASE OF ECUADOR

Abstract:

It is estimated that there are around 83 million people living at high altitudes; over 2500 meters above sea level (masl) worldwide. Andean (highlands), Tibetan, and Ethiopian populations have lived under chronic hypoxia conditions for thousands of years. From those, groups who have been residing there for over a millennium in three high-altitude zones of the globe are the Sherpa and Ayurveda (Qinghai-Tibetan Plateau), the Kichwa and Aymara highlanders (Andean Altiplano), and the Ethiopian Amhara and Oromo highlanders (the Semien Plateau in Ethiopia). For them, the adaptive and maladaptive changes have occurred at the genomic and physiological levels. In Ecuador, for example, most of the capital cities are located at altitudes above 2500 masl. High-altitude hypoxia presents numerous challenges to human health, survival, and reproduction due to the decreased oxygen availability brought on by lowered barometric pressure at high elevations. Changes in pulmonary function, arterial oxygen saturation (SaO2) hemoglobin concentration, and maternal physiology during pregnancy among others have permitted high-altitude natives to thrive in the harsh conditions. Most common adaptative changes involves ventilation rates, hypoxic ventilatory response, elevated arterial oxygen saturation, elevated hemoglobin concentration, and elevated birth weight. Despite these adaptations, it seems that some diseases are more commonly observed within these populations. For instance, the prevalence of Congenital Heart Disease (CHD) in newborns at high altitude is about 20 times higher than at low altitude. High altitude is an environmental risk factor for CHD, especially patent ductus arteriosus (PDA). By 18 months of age, about 60% of left to right shunts remain unclosed. Atrial Septal Defect (ASD), Ventricular Septal Defect (VSD) and Left Ventricular Outflow tract obstruction LVOTO are show frequently at high altitude. Researchers have tried to explain the role of high altitude on CHD for over 60 years, describing different mechanisms, including embryonic tissue hypoxia. The increase frequency of CHD at high altitudes clearly suggest a leading role for environmental mechanisms mediated by low atmospheric pressure and the persistence of pulmonary hypertension after birth. Screening newborn children for CHD) mostly focus on critical CHD using pulse oximetry. This is a review of high altitude adaptation, and its effects on CHD focused in the Andean region, and in Ecuador as a study case.