Altered cardiac β1 responsiveness in hyperthermic older adults.
Altered cardiac β1 responsiveness in hyperthermic older adults.
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改变高温老年人的心脏β1 反应性。
DOI：
10.1152/ajpregu.00040.2022
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Crandall,CraigG
中科院分区：
文献类型：
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作者：
Fischer,Mads;Moralez,Gilbert;Sarma,Satyam;MacNamara,JamesP;Cramer,MatthewN;Huang,Mu;Romero,StevenA;Hieda,Michinari;Shibasaki,Manabu;Ogoh,Shigehiko;Crandall,CraigG
与年轻人相比，老年人被动加热引起的心输出量增加减弱了约50%。这种减弱的反应可能与老年人无法通过离子型机制和/或通过改变的变时性机制来维持每搏输出量有关。本研究的目的是确定年龄和高温对多巴酚丁胺诱导的心脏刺激的心脏反应性的交互作用。11名年轻（26 ± 4岁）和8名老年（68 ± 5岁）参与者在同一天接受了常温和高温（基线核心温度+1.2 ° C）试验。在两种体温条件下，基线测量后，静脉注射多巴酚丁胺5 μg/kg/min，持续12分钟，随后15 μg/kg/min，持续12分钟。主要测量包括基于超声心动图的心脏功能评估、胃肠道和皮肤温度、心率和平均动脉压。两种热刺激条件下多巴酚丁胺对心率的反应相似（P> 0.05）。二尖瓣环收缩期峰值速度（S′），即，左心室纵向收缩功能的指数，在两种热条件下在基线时组间相似。在常温下，组间S′的增加与多巴酚丁胺给药相似。然而，当体温升高时，多巴酚丁胺可减弱老年受试者S′的增加（P< 0.001）。健康的老年人在体温过高时对多巴酚丁胺的变力性减弱，但仍保持变时性反应。这些数据表明，老年人在体温过高时通过β1-肾上腺素能机制增加心肌细胞收缩力的能力降低，这是通过S′的变化来估计的。
Compared with younger adults, passive heating induced increases in cardiac output are attenuated by ∼50% in older adults. This attenuated response may be associated with older individuals’ inability to maintain stroke volume through ionotropic mechanisms and/or through altered chronotropic mechanisms. The purpose of this study was to identify the interactive effect of age and hyperthermia on cardiac responsiveness to dobutamine-induced cardiac stimulation. Eleven young (26 ± 4 yr) and 8 older (68 ± 5 yr) participants underwent a normothermic and a hyperthermic (baseline core temperature +1.2°C) trial on the same day. In both thermal conditions, after baseline measurements, intravenous dobutamine was administered for 12 min at 5 µg/kg/min, followed by 12 min at 15 µg/kg/min. Primary measurements included echocardiography-based assessments of cardiac function, gastrointestinal and skin temperatures, heart rate, and mean arterial pressure. Heart rate responses to dobutamine were similar between groups in both thermal conditions (P> 0.05). The peak systolic mitral annular velocity (S′), i.e., an index of left ventricular longitudinal systolic function, was similar between groups for both thermal conditions at baseline. While normothermic, the increase in S′ between groups was similar with dobutamine administration. However, while hyperthermic, the increase in S′ was attenuated in the older participants with dobutamine (P< 0.001). Healthy, older individuals show attenuated inotropic, but maintained chronotropic responsiveness to dobutamine administration during hyperthermia. These data suggest that older individuals have a reduced capacity to increase cardiomyocyte contractility, estimated by changes in S′, via β1-adrenergic mechanisms while hyperthermic.