Variability of Right Ventricular Structure and Function in Infants Across Different High-Altitude Regions: ANDES-CHD-ECHO Sub-Study

Srour, MHD Osama, Darla Carvallo-Castañeda, Monica Medina, Gian Huaman, Rafael Marquez, and Katia Bravo-Jaimes.Variability of right ventricular structure and function in infants across different high-altitude regions: ANDES-CHD-ECHO sub-study. High Alt Med Biol. 00:00–00, 2026. Background: Right ventricular (RV) predominance is a normal fetal state that rapidly regresses postnatally at sea level. High-altitude hypobaric hypoxic environment may alter this adaptation process. This study evaluated echocardiographic RV variations in healthy infants across different altitudes in the Peruvian Andes. Methods: This sub-study of the ANDES-CHD cohort included 81 healthy infants from sea level to 4,338 meters (m) in Peru. RV fractional area change (FAC) and indexed RV free wall thickness were measured. Multivariate linear regression assessed the independent effect of altitude, adjusting for relevant confounders. Results: Infants at higher altitudes exhibited a statistically significant reduction in RV FAC compared with sea level (45.5% at sea level vs. 38% at 3,259 m [ p = 0.021] and 4,338 m [ p = 0.006]), though all median values remained within normal physiological ranges. Sixteen percent of infants had an RV FAC < 35%, with no significant difference between high- and low-altitude groups, and no adverse outcome at 12-month follow-up. Indexed RV free wall thickness did not differ significantly across groups. Conclusion: Healthy Andean infants demonstrate a physiological adaptation to high-altitude hypobaric hypoxia characterized by a statistical reduction in RV systolic function without pathological compromise, alongside normal postnatal regression of RV wall thickness.