Carotid Artery Structure during and after Long‐Duration Space Flight

Abstract

Space flight missions may expose astronauts to increased risk of oxidative stress and inflammatory damage induced by a variety of sources, including radiation, psychological stress, reduced physical activity, diminished nutritional status, and hyperoxic exposure during extravehicular activity. Given that evidence exists that these factors can accelerate the development of atherosclerosis, the purpose of this investigation is to determine whether long‐duration space flight (>4 months) on the International Space Station results in structural changes in the carotid artery.METHODSCarotid artery intima‐media thickness (cIMT) and diameter during systole (Ds) and diastole (Dd) were measured using standard ultrasound (VividQ, GE Healthcare) in 10 astronauts (9 M, 1 F) approximately 180 and 60 days before launch, at approximately 15 (FD15) and 60 days of flight (FD60), within two weeks before landing (R‐14), and within one week after landing. Pre‐ and post‐flight measures were obtained after the subjects had been supine for at least 20 min. Inflight measures were acquired by trained astronauts while being guided by an expert sonographer on the ground using telemedicine techniques. Carotid artery distensibility coefficient was calculated (cDC = (Ds2−Dd2)/(PP·Dd2); Gepner et al., Stroke 45: 48–53, 2014). Pre‐flight data were averaged to represent baseline. Results were analyzed using one‐way repeated measures ANOVA.RESULTSCarotid artery diameters during systole (Ds FD15: 7.6 ± 0.4; FD60: 7.6 ± 0.4; R‐14: 7.7 ± 0.4 mm; mean ± SD) and diastole (Dd FD15: 7.2± 0.3; FD60: 7.3 ± 0.4; R‐14: 7.3 ± 0.5 mm) were significantly greater during space flight than pre‐ (Ds: 7.3 ± 0.4; Dd: 6.9 ± 0.4 mm) and post‐flight (Ds: 7.4 ± 0.4; Dd: 7.1 ± 0.5 mm). There was a main effect of time on cIMT, but post‐hoc analyses did not reveal significant difference from pre‐flight (Pre: 0.58 ± 0.09 mm) at any time point (FD15: 0.58 ± 0.14; FD60: 0.54 ± 0.09; R‐14: 0.54 ± 0.09; Post: 0.62 ± 0.10 mm). Although pre‐flight cDC (0.0028 ± 0.0011/mmHg) was not different than in‐flight (FD15: 0.0023 ± 0.0011; FD60: 0.0020 ± 0.0008; R‐14: 0.0023 ± 0.0012/mmHg), post‐flight cDC (0.0019 ± 0.0010/mmHg) was significantly less than pre‐flight.CONCLUSIONSAlthough the carotid artery was distended chronically during space flight and cDC was decreased in the week after landing, in these astronauts pathological remodeling of this vessel was not evident.Support or Funding InformationSupported by the NASA Human Research Program