Healthy aging does not compromise the augmentation of cardiac function during heat stress

Daniel Gagnon, Steven A. Romero, Hai Ngo, Satyam Sarma, William K. Cornwell, Paula Y.S. Poh, Douglas Stoller, Benjamin D. Levine, Craig G. Crandall

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

During heat stress, stroke volume is maintained in young adults despite reductions in cardiac filling pressures. This is achieved by a general augmentation of cardiac function, highlighted by a left and upward shift of the Frank-Starling relation. In contrast, healthy aged adults are unable to maintain stroke volume during heat stress. We hypothesized that this would be associated with a lack of shift in the Frank-Starling relation. Frank-Starling relations were examined in 11 aged [69 ± 4 (SD) yr, 4 men/7 women] and 12 young (26 ± 5 yr, 6 men/6 women) adults during normothermic and heat stress (1.5°C increase in core temperature) conditions. During heat stress, increases in cardiac output were attenuated in aged adults (+2.5 ± 0.3 (95% CI) vs. young: +4.5 ± 0.5 l/min, P < 0.01) because of an attenuated chronotropic response (+30 ± 4 vs. young: +42 ± 5 beats/min, P < 0.01). In contrast to our hypothesis, a leftward shift of the Frank-Starling relation maintained stroke volume during heat stress in aged adults (76 ± 8 vs. normothermic: 74 ± 8 ml, P = 0.38) despite reductions in cardiac filling pressure (6.6 ± 1.0 vs. normothermic: 8.9 ± 1.1 mmHg, P < 0.01). In a subset of participants, volume loading was used to return cardiac filling pressure during heat stress to normothermic values, which resulted in a greater stroke volume for a given cardiac filling pressure in both groups. These results demonstrate that the Frank-Starling relation shifts during heat stress in healthy young and aged adults, thereby preserving stroke volume despite reductions in cardiac filling pressures.

Original languageEnglish (US)
Pages (from-to)885-892
Number of pages8
JournalJournal of Applied Physiology
Volume121
Issue number4
DOIs
StatePublished - Oct 2016

Keywords

  • Age
  • Cardiac output
  • Heart rate
  • Stroke volume

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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    Gagnon, D., Romero, S. A., Ngo, H., Sarma, S., Cornwell, W. K., Poh, P. Y. S., Stoller, D., Levine, B. D., & Crandall, C. G. (2016). Healthy aging does not compromise the augmentation of cardiac function during heat stress. Journal of Applied Physiology, 121(4), 885-892. https://doi.org/10.1152/japplphysiol.00643.2016