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 - CURIS 2022 NEXS 255

PY - 2022

Y1 - 2022

N2 - Introduction: Compared to 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.Purpose: To identify the interactive effect of age and hyperthermia on cardiac responsiveness to dobutamine induced cardiac stimulation.Methods: 11 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.Results: 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).Conclusion: Healthy, older individuals show attenuated inotropic, but maintained chronotropic responsiveness to dobutamine administration during hyperthermia. These data suggests that older individuals have a reduced capacity to increase cardiomyocyte contractility, estimated by changes in S', via β1-adrenergic mechanisms while hyperthermic.

AB - Introduction: Compared to 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.Purpose: To identify the interactive effect of age and hyperthermia on cardiac responsiveness to dobutamine induced cardiac stimulation.Methods: 11 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.Results: 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).Conclusion: Healthy, older individuals show attenuated inotropic, but maintained chronotropic responsiveness to dobutamine administration during hyperthermia. These data suggests that older individuals have a reduced capacity to increase cardiomyocyte contractility, estimated by changes in S', via β1-adrenergic mechanisms while hyperthermic.

KW - Faculty of Science

KW - Beta-adrenergic

KW - Hyperthermia

KW - Heat stress

KW - Aging

U2 - 10.1152/ajpregu.00040.2022

DO - 10.1152/ajpregu.00040.2022

M3 - Journal article

C2 - 36094450

VL - 323

SP - R581-R588

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6119

IS - 4

ER -