Unusual core temperature decrease in exercising heart-failure patients

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Abstract
Heat dissipation during exercise is presumed to be impaired in heart-failure patients due to their constricted cutaneous circulation and depressed cardiac output. Core (pulmonary artery blood) temperature and hemodynamics were studied in 16 patients with severe heart failure who performed maximal upright incremental exercise. Skin temperatures were also measured in 6 of these patients during rest and peak exercise. A normal group (n = 5 ) was exercised for comparison. In 8 of the most exercise-limited patients, core temperature was 37.10.degree. .+-. 0.63.degree. C at rest and significantly decreased at 25 W of exercise to 36.82.degree. .+-. 0.61.degree. C (P < 0.01, ANOVA [analysis of variance]). In the other 8 less exercise-limited patients, core temperature was 37.01.degree. .+-. 0.34.degree. C at rest, significantly decreased at 25 W to 36.73.degree. .+-. 0.33.degree. C (P < 0.01) and at 50 W remained decreased to 36.68.degree. .+-. 0.34.degree. C. All 16 patients returned to the control core temperature within 10 min after exercise without overshoot. In the subjects, resting core temperature was 37.11.degree. .+-. 0.41.degree. C, was the same at 25 W and significantly increased at 50 W to 37.34.degree. .+-. 0.42.degree. C (P < 0.01). Resting forearm skin temperature was significantly (P < 0.001) lower in heart-failure patients (27.10.degree. .+-. 0.08.degree. C) compared with normal subjects (31.20.degree. .+-. 0.12.degree. C) acclimated to the same ambient conditions. Apparently, heart-failure patients have an unusual core temperature decrease throughout short-term maximal exercise. This is probably caused by a redistribution of their body heat, i.e., a mixing of the core blood with the cooler contents of the cutaneous and muscle circulations.