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

11 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 1 2016

Keywords

  • Age
  • Cardiac output
  • Heart rate
  • Stroke volume

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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