Altitude-Associated Hemodynamic Alterations: Analysis from the Veterans Affairs Clinical Assessment, Reporting, and Tracking

RATIONALE: Increases in PA pressures and PVR are well-described at altitudes above 2400m. However, the potential hemodynamic implications of changes in altitude at lower elevations (<2000m) remains unexplored. OBJECTIVES: This study assessed hemodynamic changes associated with rising altitude under 2000m. METHODS: We analyzed the association of hemodynamics with altitude in a large cohort using the Veterans Affairs Clinical Assessment, Reporting, and Tracking (VA CART). Association between hemodynamic parameters and altitude was assessed using linear regression modeling, adjusting for age, sex, and body mass index. MEASUREMENTS AND RESULTS: The study included 91,128 patients undergoing RHC at 76 centers at altitudes between 0m-1640m. For every SD increase in altitude (364m), mean PA pressure (0.4 ±0.07 mmHg) and PVR (0.06 ± 0.01 WU) increased. The likelihood of meeting criteria for pulmonary hypertension (PH), specifically pre-capillary PH and combined pre- and post-capillary pulmonary hypertension, increased with altitude. For patients with reduced left ventricular systolic function (EF < 40%), we found that the likelihood of having a PVR >3WU increased with altitude. Patients with EF < 40% at ≥ 1000m elevation were 22% more likely to have a PVR >3 WU than those at < 500m (OR 1.22 95% CI 1.10-1.36; p < 0.001). Pulmonary vascular compliance did not change with altitude, and the pulmonary resistance-compliance relationship was shifted upward and to the right at higher altitude. CONCLUSIONS: Modest increases in altitude (between 0-1640m) are associated with clinically significant alterations in pulmonary artery hemodynamics. Such changes may impact PH diagnosis and classification and eligibility for advanced cardiovascular interventions.