Elevated echocardiographic pulmonary to left atrial ratio (ePLAR) in high-altitude residents

Population-specific reference values for the echocardiographic pulmonary to left atrial ratio (ePLAR) are lacking for high-altitude residents. This study aimed to establish ePLAR reference values for healthy individuals at extreme high altitude and identify its key determinants.

In this cross-sectional study, we enrolled 120 healthy adults (aged 18-75 years) permanently residing at an altitude of ≥4,000 meters and 120 age- and sex-matched lowland controls (≤5 meters). All participants underwent comprehensive echocardiography. The ePLAR (m/s) was calculated as the ratio of peak tricuspid regurgitation velocity (TRV_max) to the mitral E/e' ratio. Clinical and laboratory data were systematically collected. Multivariable regression analysis identified independent ePLAR determinants in the high-altitude cohort.

High-altitude residents demonstrated significantly higher ePLAR values compared to lowlanders [0.31 (0.23-0.39) vs. 0.20 (0.15-0.28) m/s, P<0.0001]. Multivariable analysis identified tricuspid annular plane systolic excursion (TAPSE; β=-0.251, P<0.001), hemoglobin concentration (β=0.151, P=0.023), age (β=0.169, P=0.007), sex (β=-0.204 for males, P=0.003), body mass index (BMI; β=-0.183, P=0.001), and systolic blood pressure (SBP; β=-0.239, P<0.001) as independent determinants of ePLAR (adjusted R²=0.186, P<0.0001).

This study establishes the first ePLAR ranges for extreme high-altitude populations, which are substantially elevated compared to lowland values. The ePLAR is independently determined by cardiopulmonary (TAPSE), hematological (hemoglobin), and demographic factors (age, sex, BMI, SBP). These altitude-specific benchmarks are essential for cardiovascular risk assessment and pulmonary hypertension screening in high-altitude populations.