P9.09 LARGE ARTERY FUNCTION AND VENTRICULAR ARTERIAL COUPLING DURING PROLONGED BED REST

Abstract

Background: prolonged circulatory unloading associated with head-down tilt bed rest (HDTBR) is followed by cardiovascular deconditioning. Aim of the study was to investigate to what extent large artery function and arterial-ventricular coupling (VA) are involved. Methods: ten healthy male volunteers (age 23±2) were studied before and after a 35-day HDTBR. Left ventricular (LV) volumes were investigated by echocardiography; carotid diameter and intima media thickness were assessed by high resolution ultrasound (Q-IMT, Esaote Europe). Contour Wave Analysis, performed by tonometer (PulsePen, DiaTecne, Milan Italy), was used to explore large artery function. Carotid-femoral pulse wave velocity (PWV) was also estimated (Complior, Alam, Paris). Results: no changes were observed for systolic and diastolic blood pressure, PWV and QIMT vs baseline, while LV volumes showed a significant reduction (p<0.05). Arterial Elastance (Ea= end systolic pressure/stroke volume) and LV Elastance (Elv= end systolic pressure (ESP)/end systolic volume (ESV)) increased after HDTBR (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). Contour wave analysis showed no significant changes for Augmentation Index (Aix), a reduction for PPI (Pulse Pressure Index: pulse pressure/mean arterial pressure, from 0.55±0.14 to 0.45±0.09, p<0.05), SEVR (subendocardial variability ratio: 1.84±0.33 vs 1.55±0.25, p=0.008) and LVET (left ventricular ejection time: 304.6±19.8 vs 291.5±11.2 ms, p=0.05), and an increase in heart rate (from 58±2 to 73±6, p<0.05). Conclusions: no significant alterations in intrinsic arterial stiffness and structure were detected after HDTBR. The observed changes in large arteries function appear secondary to changes in LV performance.