title: Effects of heat stress on thermoregulatory responses in congestive heart failure patients.
abstract: BACKGROUND
  Clinical observations suggest that tolerance to heat stress may be impaired in patients with cardiovascular diseases, particularly those associated with impaired ventricular function and congestive heart failure (CHF). However, thermoregulatory function during a controlled heat stress challenge in patients with CHF has not been studied.
  
  
  RESULTS
  To test the hypothesis that thermoregulatory responses are attenuated in such patients, we assessed cutaneous vasodilation and sweat rate in patients with stable class II-III CHF and in matched healthy subjects during passive whole-body heating. Whole-body heating induced a similar increase in internal temperature (approximately 0.85 degrees C) in both groups. The sweating responses in patients with CHF were not significantly different from that in control subjects. In contrast, the elevation in forearm cutaneous vascular conductance in patients with CHF was reduced by nearly 50% relative to the control subjects (3.8+/-0.8 versus 6.9+/-1.0 mL/100 mL tissue per minute per 100 mm Hg, P=0.04). Moreover, maximal cutaneous vasodilator capacity to direct local heating in patients with CHF was also significantly lower than in control subjects, suggesting that vascular remodeling may be limiting cutaneous vasodilation during hyperthermia.
  
  
  CONCLUSIONS
  These observations suggest that patients with CHF exhibit attenuated cutaneous vasodilator responses to both whole-body and local heating, whereas sweating responses are preserved. Attenuated cutaneous vasodilation may be a potential mechanism for heat intolerance in patients with CHF.
authors.affiliation: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, TX 75231, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Cui
authors.forename: Armin
authors.initials: A
authors.lastname: Arbab-Zadeh
authors.forename: Anand
authors.initials: A
authors.lastname: Prasad
authors.forename: Sylvain
authors.initials: S
authors.lastname: Durand
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Levine
authors.forename: Craig G
authors.initials: CG
authors.lastname: Crandall
mesh_terms: D001833:Body Temperature Regulation; D004452:Echocardiography; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D018882:Heat Stress Disorders / Q000150:complications* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D014664:Vasodilation