TY - JOUR
T1 - Altered cardiac β1 responsiveness in hyperthermic older adults
AU - Fischer, Mads
AU - Moralez, Gilbert
AU - Sarma, Satyam
AU - MacNamara, James P.
AU - Cramer, Matthew N.
AU - Huang, Mu
AU - Romero, Steven A.
AU - Hieda, Michinari
AU - Shibasaki, Manabu
AU - Ogoh, Shigehiko
AU - Crandall, Craig G.
N1 - Funding Information:
This work was supported in part from National Institute of General Medical Sciences Grant R01GM068865 and National Institute on Aging Grant R01AG069005 (to Craig G. Crandall). M. Fischer is supported by funding from the European Union’s Horizon 2020 research and innovation program under the grant agreement No 668786.
Funding Information:
We sincerely thank the study volunteers for their participation. Present address of M. N. Cramer: Defense Research and Development Canada, Toronto Research Center, Toronto, ON, Canada. This work was supported in part from National Institute of General Medical Sciences Grant R01GM068865 and National Institute on Aging Grant R01AG069005 (to Craig G. Crandall). M. Fischer is supported by funding from the European Union’s Horizon 2020 research and innovation program under the grant agreement No 668786.
Publisher Copyright:
Copyright © 2022 the American Physiological Society.
PY - 2022/10
Y1 - 2022/10
N2 - 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 mg/kg/min, followed by 12 min at 15 mg/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.
AB - 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 mg/kg/min, followed by 12 min at 15 mg/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.
KW - aging
KW - heat stress
KW - hyperthermia
KW - β -adrenergic
UR - http://www.scopus.com/inward/record.url?scp=85140271958&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.00040.2022
DO - 10.1152/ajpregu.00040.2022
M3 - Article
C2 - 36094450
AN - SCOPUS:85140271958
SN - 0363-6119
VL - 323
SP - R581-R588
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 4
ER -