Is Syncope Related to Moderate Altitude Exposure?

STUDY OBJECTIVE: To investigate factors related to syncope occurring on recent ascent to moderate altitude. DESIGN: A 1-year retrospective case-control study, using local acclimatized residents as a control group. SETTING: The two main ambulance destinations for Summit County, Colorado (elevation, 2770 m). PATIENTS: All patients with a diagnosis of syncope, near-syncope, or fainting whose medical records were available for review. RESULTS: There was a significant relationship (P less than .05) between syncope of unknown origin and recent arrival at altitude (less than 24 hours), and a significant inverse relationship (P less than .05) between syncope of unknown origin and arterial oxygen saturation as measured by pulse oximetry. CONCLUSIONS: Short-term exposure to moderate altitude may be related to otherwise unexplained syncope in healthy young adults. We suggest the name high-altitude syncope for this entity and encourage further research in this area.