The relationship between cardiovascular reactivity in the laboratory and heart rate response in real life: active...

Earlier studies suggest that cardiovascular responses in the laboratory and in the field are likely to be related when the laboratory tasks involve active coping, when the field measure is taken continuously, and when there is allowance for the effects of autocorrelation and physical activity on the ambulant cardiovascular measure. These studies lead to the hypothesis that the hyperreactivity common to the laboratory and to the field has a beta-adrenergic basis. We examined the heart rate variability of 16 hyperreactive and 16 hyporeactive subjects over an 8-hour period while they were receiving either a placebo or a cardio-selective beta-blocking drug (Bisoprolol) in a double-blind crossover design. Subjects were classified on the basis of their heart rate and systolic blood pressure responses to a complex self-paced, reaction-time task. Response in the field was assessed from the standard deviation of the raw heart rate series, after allowance for the serial dependency in the data using autoregressive methods and, when allowance was made for physical activity, assessed from the muscle activity of the thigh. As predicted, on placebo hyperreactive subjects had markedly more variable heart rates, particularly when allowance was made for physical activity. Although not confirmed by a significant interaction effect, this difference largely disappeared under beta-blockade.