Exaggerated pulmonary hypertension and right ventricular dysfunction in high-altitude dwellers with patent foramen ovale.

BACKGROUND: There is considerable inter-individual variability of pulmonary artery pressure among high altitude dwellers, but the underlying mechanism is not known. At low altitude, a patent foramen ovale (PFO) is present in ~25% of the general population. Its prevalence is increased in clinical conditions associated with pulmonary hypertension and arterial hypoxemia and thought to aggravate these problems. METHODS: We searched for a PFO (transesophageal echocardiography) in healthy high altitude dwellers (n=22) and patients with chronic mountain sickness (n=35) at 3600 m above sea level and studied its effects (transthoracic echocardiography) on right ventricular function, pulmonary artery pressure and vascular resistance at rest and during mild exercise (50 W), an intervention designed to further increase pulmonary artery pressure. RESULTS: The prevalence of PFO (32 %) was similar to the one reported in low altitude populations and was not different in participants with/without chronic mountain sickness. Its presence was associated with right ventricular enlargement at rest and an exaggerated increase in right-ventricular-to-right-atrial pressure gradient (25±7 vs. 15±9 mm Hg, p<0.001) and a blunted increase of fractional area change of the right ventricle (3 [-1, 5] vs 7 [3, 16] %, p=0.008) during mild exercise. CONCLUSION: These findings show for the first time that while the prevalence of PFO is not increased in high altitude dwellers, its presence appears to facilitate pulmonary vasoconstriction and right ventricular dysfunction during a mild physical effort frequently associated with daily activity. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01182792.