Background: prolonged head-down tilt bed rest (HDTBR) is followed by a decrease in circulating volume possibly affecting large artery structure and function. Aim of the study was to investigate common carotid artery (CCA) remodelling and ventricular-arterial (VA) coupling after HDTBR. Methods: ten healthy male volunteers (age 23 +/- 2) were studied before and after a 35-day HDTBR. Ultrasound (Esaote MyLab30) was used to estimate LV volumes, transmitral and aortic flow velocity (FV), CCA diameter and FV, high resolution IMT (Q-IMT). Applanation tonometry (PulsePen, DiaTecne), was used to explore large artery dynamics and wave reflection (WR). Carotid-femoral pulse wave velocity (PWV) was also estimated (Complior, Alam). Results: no changes were observed for central BP vs baseline, while LV volumes and stroke volume significantly decreased and HR increased (from 58 +/- 2 to 73 +/- 6, p < 0.05). Myocardial performance index (MPI), a Doppler derived index of global LV function [isovolumic contraction time+isovolumic relaxation time)/LV ejection time], increased after HDTBR (0.71 +/- 0.12 vs 0.52 +/- 0.06, p < 0.005), as well as arterial elastance (Ea = end systolic pressure/stroke volume) and LV elastance [Elv = end systolic pressure (ESP)/end systolic volume (ESV)] (for Ea: 1.08 +/- 0.198 vs 1.31 +/- 0.21, p = 0.01; for Elv 1.478 +/- 0.32 vs 1.765 +/- 0.42, p = 0.04), with unchanged Ea/Elv (0.74 +/- 0.09 vs 0.76 +/- 0.1). PWV, CCA diameter, systolic FV and QIMT did not change, while diastolic and mean FV significantly increased (p < 0.05: FVd from 25 +/- 4 to 29 +/- 4 cm/s, FVm from 42 +/- 8 to 52 +/- 11 cm/s). Pulsatility index [PI = (peak systolic velocity-diastolic velocity)/Mean velocity] decreased from 2.3 +/- 0.3 to 1.9 +/- 0.2, p < 0.02). Applanation tonometry showed no significant changes for Augmentation Index (AIx) and time to WR, while PPI (Pulse Pressure Index: PP/MBP) decreased from 0.55 +/- 0.14 to 0.45 +/- 0.09, p < 0.05). Conclusions: after prolonged HDTBR, a reduction in LV pump function is observed with unchanged VA coupling. No significant changes are found in intrinsic arterial stiffness, CCA remodelling and WR, while changes in arterial dynamics indicate a reduction in the pulsatile component and an increase in the steady component of BP, possibly associated with reduced circulating volume and increased peripheral vasodilation.

Large artery function and ventricular arterial coupling following cardiovascular unloading related to prolonged bed rest in young healthy subjects.

PALOMBO, CARLO;
2010-01-01

Abstract

Background: prolonged head-down tilt bed rest (HDTBR) is followed by a decrease in circulating volume possibly affecting large artery structure and function. Aim of the study was to investigate common carotid artery (CCA) remodelling and ventricular-arterial (VA) coupling after HDTBR. Methods: ten healthy male volunteers (age 23 +/- 2) were studied before and after a 35-day HDTBR. Ultrasound (Esaote MyLab30) was used to estimate LV volumes, transmitral and aortic flow velocity (FV), CCA diameter and FV, high resolution IMT (Q-IMT). Applanation tonometry (PulsePen, DiaTecne), was used to explore large artery dynamics and wave reflection (WR). Carotid-femoral pulse wave velocity (PWV) was also estimated (Complior, Alam). Results: no changes were observed for central BP vs baseline, while LV volumes and stroke volume significantly decreased and HR increased (from 58 +/- 2 to 73 +/- 6, p < 0.05). Myocardial performance index (MPI), a Doppler derived index of global LV function [isovolumic contraction time+isovolumic relaxation time)/LV ejection time], increased after HDTBR (0.71 +/- 0.12 vs 0.52 +/- 0.06, p < 0.005), as well as arterial elastance (Ea = end systolic pressure/stroke volume) and LV elastance [Elv = end systolic pressure (ESP)/end systolic volume (ESV)] (for Ea: 1.08 +/- 0.198 vs 1.31 +/- 0.21, p = 0.01; for Elv 1.478 +/- 0.32 vs 1.765 +/- 0.42, p = 0.04), with unchanged Ea/Elv (0.74 +/- 0.09 vs 0.76 +/- 0.1). PWV, CCA diameter, systolic FV and QIMT did not change, while diastolic and mean FV significantly increased (p < 0.05: FVd from 25 +/- 4 to 29 +/- 4 cm/s, FVm from 42 +/- 8 to 52 +/- 11 cm/s). Pulsatility index [PI = (peak systolic velocity-diastolic velocity)/Mean velocity] decreased from 2.3 +/- 0.3 to 1.9 +/- 0.2, p < 0.02). Applanation tonometry showed no significant changes for Augmentation Index (AIx) and time to WR, while PPI (Pulse Pressure Index: PP/MBP) decreased from 0.55 +/- 0.14 to 0.45 +/- 0.09, p < 0.05). Conclusions: after prolonged HDTBR, a reduction in LV pump function is observed with unchanged VA coupling. No significant changes are found in intrinsic arterial stiffness, CCA remodelling and WR, while changes in arterial dynamics indicate a reduction in the pulsatile component and an increase in the steady component of BP, possibly associated with reduced circulating volume and increased peripheral vasodilation.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/141370
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