Muscle sympathetic nerve activity response to heat stress is attenuated in chronic heart failure patients.
Heat stress evokes significant increases in muscle sympathetic nerve activity (MSNA) in healthy individuals. The MSNA response to heat stress in chronic heart failure (CHF) is unknown. We hypothesized that the MSNA response to heat stress is attenuated in CHF. Passive whole body heating was applied with water-perfused suits in 13 patients (61 ± 2 yr) with stable class II-III CHF, 12 age-matched (62 ± 2 yr) healthy subjects, and 14 young (24 ± 1 yr) healthy subjects. Mild heating (i.e., increases in skin temperature ΔTsk ~2-4°C, internal temperature ΔTcore <0.3°C) significantly decreased MSNA in CHF patients; however, it did not significantly alter the MSNA in the age-matched and young healthy subjects. Heat stress (i.e., ΔTsk ~4°C and ΔTcore ~0.6°C) raised MSNA in the age-matched (32.9 ± 3.2 to 45.6 ± 4.2 bursts/min;P< 0.001) and young (14.3 ± 1.7 to 26.3 ± 2.4 bursts/min;P< 0.001) controls, but not in CHF (46.2 ± 5.3 to 50.5 ± 5.3 bursts/min;P= 0.06). The MSNA increase by the heat stress in CHF (Δ4.2 ± 2.0 bursts/min) was significantly less than those seen in the age-matched (Δ12.8 ± 1.7 bursts/min,P< 0.05) and young (Δ12.0 ± 2.7 bursts/min,P< 0.05) control groups. These data suggest that the MSNA response to heat stress is attenuated in CHF patients. We speculate that the attenuated MSNA response to heat stress may contribute to impaired cardiovascular adjustments in CHF in a hot environment.
Penn State Heart and Vascular Institute, Penn State Hershey, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Jian
J
Cui
Penn State Heart and Vascular Institute, Penn State Hershey, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
John
J
Boehmer
Penn State Heart and Vascular Institute, Penn State Hershey, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Cheryl
C
Blaha
Penn State Heart and Vascular Institute, Penn State Hershey, Milton S. Hershey Medical Center, Hershey, Pennsylvania lsinoway@hmc.psu.edu.
Lawrence I
LI
Sinoway
D000200:Action Potentials; D000328:Adult; D000367:Age Factors; D017704:Baroreflex; D001833:Body Temperature Regulation; D016022:Case-Control Studies; D002908:Chronic Disease; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology*; D018882:Heat Stress Disorders / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D010543:Peroneal Nerve / Q000503:physiopathology*; D012881:Skin Temperature; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
heart failure; hemodynamics; nervous system; stress; sympathetic