Reduced baroreflex control of heart rate during lower body negative pressure and carotid arterial wall characteristics in the elderly

点击翻译按钮获取中文摘要

The purpose of this study was to compare arterial baroreflex control of heart rate (HR) during a central hypovolemic stress in the elderly and young males. Healthy old (68±1 y) and young (20±0 y) men underwent a graded lower body negative pressure (LBNP) for the hypovolemic stress. The baseline values of baroreflex sensitivity (BRS) of HR evaluated by the sequence method were similar in both groups. During LBNP (〜60 mm Hg), BRS of HR was attenuated in the young, however, there was no change in the old males. There is a possibility that there are some impairments of baroreflex arc function including the distensibility of vascular where baroreceptors are in the old during LBNP.To delineate the relationship between the distensibility of carotid artery and BRS of HR, the next step of this study was carried out to examine both carotid arterial wall characteristics and BRS of HR. Ten each of healthy young (22±1 y) and old (69±1 y) men underwent to measure ultrasonographically the carotid intima-media thickness (IMT), carotid arterial lumen diameter and its change with arterial pulse. Blood pressure (BP) was measured with an applanation tonometry at the carotid artery. BRS of HR was evaluated by a bolus injection of phenylephrine (rising arterial pressure) or sodium nitroprusside (falling arterial pressure). The carotid IMT was higher in the old than in the young, whereas, baseline compliance of the carotid artery was less in the old than the young. No age-related difference was detected in the baseline level of carotid systolic blood pressure. The BRS of HR was less in the old compared to the young during both rising and falling pressures. The IMT or the baseline compliance of carotid artery was related to BRS of HR (p<0.05). These results suggest that an increase in IMT occurs in concurrence with a reduction of compliance and the baroreflex control of HR during baseline and hypovolemic stress in the elderly.