Evaluation of the effects of 60-days Head-Down Bed Rest and Nutritional Countermeasure on cardiac circadian rhythms
- Paper number
IAC-19,A1,2,3,x49056
- Author
Ms. Sarah Solbiati, Italy, Politecnico di Milano
- Coauthor
Ms. Martina Turcato, Italy, Politecnico di Milano
- Coauthor
Ms. Alba Martin-Yebra, Sweden, Lund University
- Coauthor
Dr. Lorenzo Costantini, Italy
- Coauthor
Prof. Pierre Vaïda, France, Université Bordeaux Segalen
- Coauthor
Ms. Federica Landreani, Italy
- Coauthor
Prof.Dr. Enrico Gianluca Caiani, Italy, Politecnico di Milano
- Year
2019
- Abstract
Aims. Prolonged weightlessness exposure associated to space flight generates cardiac deconditioning, with potential implications on ECG circadian rhythms. Head-down (-6 degrees) bed-rest (HDBR), as model of chronic circulatory unloading, simulates sustained microgravity exposure. We aimed at evaluating the impact of 60-days HDBR on beat-by-beat RR and ventricular repolarization (QTend) duration circadianity and the effectiveness of nutritional countermeasure (CM). Methods. 20 males (34$\pm$7 years), enrolled at MEDES (Toulouse, France) after study ethical approval and signed informed consent, were randomly allocated into a CM group (N=10), undergoing daily nutritional vitamin and antioxidant cocktail supplementation during HDBR, or control group (CTRL, N=10). Day (7AM-11PM) and night (11PM-7AM) cycle was imposed. For each subject, 12-leads 24-hours Holter ECG (1000 Hz, H12+, Mortara Instrument Inc.) was acquired 9 days before HDBR (BCD-9), the 5th (HDT5), 21st (HDT21) and 58th (HDT58) day of HDBR, the first (R+0) and 8th (R+7) day after HDBR. For each extracted 24h RR and QTend beat-to-beat series, circadianity was evaluated by Cosinor analysis, resulting in MESOR (Midline Statistic of Rhythm), oscillation amplitude (OA, measuring half variation within a night-day cycle), and acrophase (temporal value at the maximal amplitude of the fitting sinusoid). Statistical analysis was applied to test the effects of 60-days HDBR versus BCD-9 (Wilcoxon, p$<$0.05), and to compare CTRL and CM (Mann-Withney, p$<$0.05). Results. Compared to BCD-9, at HDT5, RR (CTRL:+17.4\%, CM:+16.6\%) and QTend (CTRL:+3.5\%, CM:+1.7\%) MESOR showed the maximum increment, with RR MESOR then recovering along HDBR (CTRL:+11.4\% at HDT21, CM:-2.2\% at HDT58). Conversely, compared to BCD-9, at R+0 an abrupt decrease was visible both in RR (CTRL:-21.4\%, CM:-27\%) and QTend (CTRL:-9\%, CM:-10.9\%), with a trend to baseline values at R+7. During HDBR, OA decreased in both RR (CM:-43.4\% at HDT21, higher than CTRL:-28.5\%), and QTend (CM up to 48.7\% at HDT58). Post-BR, OA restored to baseline, except for QTend in CTRL at R+0 (+33.2\%). Acrophase was shifted backward during HDBR (CTRL:-3.2\% and CM:-5.3\% at HDT5), and postponed at R+0 compared to BCD-9 (CTRL: RR 4:19AM[4:06;4:42] versus 4:00AM[3:30;4:12]; QTend 4:36AM[4:12;4:54] versus 4:12AM[3:42;4:30]). Circadianity uncoupling between RR and QTend, as difference between acrophases, was found in CTRL at HDT5 (-4'56"[-13'54";1'53"]) compared to BCD-9 (15'57"[8'36";23']), and in CM at HDT58 (-1'[-12';20'36"] versus 0'54"[-5';30'36"]). Conclusions. 60-days HDBR affects ECG circadian rhythms notwithstanding the nutritional countermeasure, by reducing amplitude and altering acrophase, differently in RR and QTend. The observed changes appeared reversible and within physiologic limits.
- Abstract document
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