P166 HEAD-DOWN TILT BED-REST SIGNIFICANTLY INCREASES CENTRAL ARTERIAL STIFFNESS

Abstract

The vascular system is subject to continual variation in mechanical stresses, both physiological and pathological. Vascular remodeling via changes in vessel wall properties, including thickness and stiffness, is a major feature of aging and cardiovascular disease. A more detailed understanding of the interplay between mechanical stress, aging, CVD and vascular remodeling will aid prevention of increased cardiovascular risk following long term microgravity. This study aims at assessing vascular remodeling processes resulting from a 60-day head-down-tilt bed-rest period during the European Space Agency Study (Toulouse, France). We hypothesize that arterial remodeling processes are modified by long term bed- rest and constitute a significant cardiovascular risk in the long term for astronauts. Applanation tonometry is used to assess carotid to femoral pulse wave velocity (PWV) and non-invasive ultrasound imaging are used to assess arterial remodelling processes at the carotid, femoral, brachial and popliteal arteries.Measurements are performed at baseline; at day 29 and 52 of bed-rest; and at day 6 and 30 of the recovery period. The preliminary results including 10 first subjects, demonstrate a strong effect of bed- rest on arterial PWV.The average PWV at baseline equals 7,6±1.4m/s and is increased to 9.0±1.9m/s after 29 days, and, 9.3±1.8m/s after 52 days bed-rest. This increase is significantly different between baseline, and, 29 and 52 days bed-rest (p < 0.005). Increase in PWV suggests a rapid and significant stiffening of the central arteries, which on healthy subjects corresponds to an aging process wich occurs many years. Low gravity conditions as during bed-rest induce significant arterial stiffening that could be linked to long term CVD risks for either patients in bed-rest or astronauts.