Stimulus-Specific Patterns of Cardiovascular Reactivity in Type A and B Subjects: Evidence for Enhanced Vagal Reactivity in Type B

Recent evidence suggests that the differences in cardiovascular reactivity between individuals exhibiting the Type A behavior pattern and those that do not are not limited to excessive betaadrenergic reactivity in Type A's. Research also suggests the possibility of a tendency for enhanced alpha-adrenergically and vagally mediated cardiovascular reactivity in Type B's. In the present study, Type A and Type B subjects were exposed to stressor stimuli known to elicit either betaadrenergic or alpha-adrenergic and vagal responses in the cardiovascular system. Heart rate, blood pressure, and forearm blood flow and vascular resistance responses were measured. The two Types did not differ in response to the beta-adrenergic stimulus (mental arithmetic). However, the alpha-adrenergic/vagal stimulus (cold face stimulus) produced more prolonged heart rate and blood flow responses in Type B subjects. Results suggest that Type B's show hyperreactivity (compared to Type A) when alpha-adrenergic or vagal cardiovascular responses are elicited. The nature of this hyperreactivity suggests possible mechanisms for reduced cardiovascular disease risk in Type B individuals.