CAROTID WALL STRUCTURE DURING and AFTER 6 MONTHS SPACEFLIGHT

Philippe L ARBEILLE^1,2*Kathryn Zuj^1,2Danielle Greaves³Richard Hughson³

• ¹Unité de Médecine et Physiologie Spatiales (UMPS-CERCOM), Centre Hospitalier Universitaire Trousseau de Tours, Tours, France
• ²Universite de Tours, Tours, France
• ³University of Waterloo, Waterloo, Canada

Purpose: Long-duration spaceflight has been shown to result in vascular adaptation. However, little is known about the recovery of these parameters after the flight. The purpose of our study was to assess common carotid (CC) artery wall properties before, during, and after six months of spaceflight on the International Space Station (ISS).Methods: CC artery wall properties were assessed using ultrasound measures of the intima media thickness (IMT) and the evaluation of the radiofrequency signal to determine the index of reflectivity (IR) for the posterior wall, posterior intima, and neck muscle. Data were collected from ten astronauts preflight (PRE), on flight day 150 (FD150), four days (R+4), and six months postflight (R+6m).Results: IMT was increased from PRE (0.56 ± 0.09 mm) on FD150 (0.65 ± 0.11 mm) and R+4 (0.65 ± 0.08 mm) and returned to PRE levels on R+6m (0.57 ± 0.12 mm). Posterior wall IR also increased from PRE (63 ± 5.5 %) on FD150 (78 ± 7.8 %) and R+4 (86 ± 4.4 %) and returned to PRE levels on R+6m (60 ± 23%). In contrast, intima IR and neck muscle IR both increased slightly during spaceflight but returned to preflight levels on R+4. Conclusion: Changes in CC posterior wall IMT and IR that persisted at R+4 but normalized at R+6m suggest structural or content modifications of the vessel wall. In contrast, the early recovery of neck muscle and posterior wall intima IR at R+4 suggests a transient process possibly related to microgravity induced fluid shifts.