Impaired skin blood flow response to environmental heating in chronic heart failure.
OBJECTIVE
We examined the thermoregulatory response to heat exposure in patients with chronic heart failure.


RESULTS
Skin blood flow (SkBF) was measured in HF subjects and matched controls. Cutaneous vascular conductance (CVC) was calculated from laser-Doppler SkBF and blood pressure. To assess the nitric oxide contribution to thermoregulatory responses, subcutaneous microdialysis membranes were placed beneath the laser-Doppler probes to infuse N(G)-nitro-l-arginine methyl ester (l-NAME), or Ringer's solution. Core (T(C)) and skin temperatures (five sites, T(Sk)) were continuously recorded. Subjects were studied during normothermia then at 38 degrees C, 50%RH within a climate chamber. T(C) and T(Sk) did not differ between HF and controls during normothermia and heating induced similar increases in both groups. During heating, CVC rose in both groups, but significantly less so in HF (HF 43.9+/-7.8 vs. controls 58.0+/-7.5% CVC(max), P<0.05). l-NAME attenuated SkBF responses in the control (58.0+/-7.5 vs. 34.6+/-5.1% CVC(max), P<0.001) and HF subjects (43.9+/-7.8 vs. 27.0+/-2.2% CVC(max), P<0.005), with a larger effect evident in the controls (P<0.05).


CONCLUSIONS
HF patients exhibit impaired thermoregulatory responses to heat exposure. Lower SkBF in HF, which defends blood pressure during heat exposure, also predisposes these subjects to heat intolerance.
Green
Daniel J
DJ
School of Human Movement and Exercise Science, The University of Western Australia, Crawley 6009, Nedlands, Western Australia. brevis@cyllene.uwa.edu.au
Maiorana
Andrew J
AJ
Siong
Jeffrey Ha Jin
JH
Burke
Valerie
V
Erickson
Matthew
M
Minson
Christopher T
CT
Bilsborough
William
W
O'Driscoll
Gerry
G
D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000502:physiology; D002908:Chronic Disease; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006333:Heart Failure / Q000503:physiopathology*; D006361:Heating; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D012867:Skin / Q000098:blood supply*; D014664:Vasodilation / Q000502:physiology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester