Pulmonary haemodynamics and right heart function during exercise at high versus low altitude in patients with pulmonary vascular disease: a randomised crossover trial

Background Patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension (PAH/CTEPH) may experience physiological stress at high altitude. We investigated pulmonary haemodynamics and right heart function during incremental (IET) and constant work-rate exercise tests (CWRET) at high (2500 m) vs low altitude (470 m). Methods In this randomised crossover trial, patients with stable PAH/CTEPH without resting hypoxaemia performed IET and CWRET at both altitudes. Systolic pulmonary arterial pressure (sPAP) and right ventricular (RV) arterial coupling (tricuspid annular plane systolic excursion/sPAP) were assessed by echocardiography. Results Among 27 patients (44% women, 61±14 years), sPAP was higher at rest at 2500 m vs 470 m (mean difference: 14 mm Hg, 95% CI 7 to 23), but increased linearly during exercise with similar slopes at each altitude (7.9 vs 9.7 mm Hg/min, respectively). RV arterial coupling was lower at high altitude at rest (difference: −0.13 mm/mm Hg, 95% CI −0.26 to −0.04) but decreased comparably during exercise. During CWRET, sPAP rose steeply in the first 3 min, plateauing thereafter, with no altitude-dependent differences in pressure-flow slope. Oxygen delivery was reduced at high altitude. Conclusion Despite higher baseline sPAP and reduced RV coupling at rest, exercise-induced haemodynamic changes were similar at both high and low altitudes, suggesting short-term altitude exposure does not exacerbate cardiopulmonary stress during exercise in stable PAH/CTEPH. The exercise protocol (IET vs CWRET) alters haemodynamic trajectories more than altitude. Trial registration number NCT05107700 .