CONSISTENCY OF HEART-RATE AND SYMPATHOVAGAL REACTIVITY ACROSS DIFFERENT AUTONOMIC CONTEXTS

Theories that psychophysiological reactivity constitutes a risk factor for coronary artery disease assume that reactivity is a consistent in dividual characteristic. We tested this assumption by measuring reacti vity to three psychologically challenging tasks performed by 22 health y subjects across different autonomic contexts produced by positional change. Dependent variables included heart rate (HR), low-frequency (L F; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.50 Hz) heart period va riability, and the LF/HF ratio. HR (r =.44, p <.05) and LF/HF ratio (r =.48, p =.03) reactivity were modestly correlated across the differen t autonomic contexts, but HF and LF power reactivity were not. These f indings suggest that HR reactivity to psychological challenge is a mod estly consistent characteristic of individuals, despite differences in autonomic context. Although the same is true of cardiac sympathovagal balance, reactivity of HF and LF power were less consistent.