Effects of a Sea-Level Stay on Pulmonary Hemodynamics in Patients With Pulmonary Arterial Hypertension Living in Quito Near 2,850 m

BACKGROUND: Among the > 80 million people living > 2,500 m are patients with pulmonary arterial hypertension (PAH). RESEARCH QUESTION: How does descent to sea level (SL) affect pulmonary hemodynamics and 6-minute walk distance (6MWD) in patients with PAH living at high altitude (HA)? STUDY DESIGN AND METHODS: ), 6MWD, systolic pulmonary artery pressure (sPAP), cardiac output (CO), and other measures were assessed at 2,850 m and after the first night (day 2) and second night (day 3) at SL. RESULTS: was higher (+5.5% [3.9%-7.1%], sPAP and HR were lower (-11 [-16 to -5] mm Hg and -7 [-12 to -3] bpm) (all P < .001), resulting in unchanged sPAP/CO and oxygen delivery. HR and CO further decreased on day 3, resulting in unchanged sPAP/CO vs HA. 6MWD was higher at SL vs HA on day 2 (+41 [16-67] m; P < .001) but not day 3. No adverse events occurred, including after re-ascent. INTERPRETATION: Our results show that typical patients with PAH living at 2,850 m reveal improved blood oxygenation after descent to SL along with decreased sPAP, but also HR, resulting in unchanged pulmonary resistance and oxygen delivery. Although 6MWD initially increased at SL, it returned to high-altitude baseline after the second night, along with further HR and CO decrease. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; Nos.: NCT06092424, NCT05996302; URL: www. CLINICALTRIALS: gov.