Comparative effects of two beta-blockers on cardiovascular reactivity and type A behavior in hypertensives

This study compared the effects of beta-blockers differing in degree of central nervous system penetration on Type A behavior and cardiovascular reactivity to mental stress. Forty-six male hypertensives were assigned randomly to receive either highly lipophilic and nonselective propranolol, hydrophilic and cardioselective atenolol, the diuretic hydrochlorothiazide, or placebo. Subjects were administered parallel forms of the Structured Interview (SI) and performed mental arithmetic and a cognitive task prior to and after 6 weeks of therapy. Results indicated that diuretic and placebo subjects (subsequently combined into a single control group) did not differ and that both beta-blockers reduced heart rate but not blood pressure reactivity to mental stress (p less than 0.02), an effect that was strongest during the mental arithmetic test. Analysis of SI components indicated a reduction only in explosive speech for beta-blockers versus controls (p less than 0.05). For global SI classifications, seven out of 12 subjects (58%) receiving propranolol, three of 12 (25%) receiving atenolol, and four of 22 control subjects (18%) became less Type A (p less than 0.05). These data do not replicate results of a prior study obtained with atenolol and suggest that only a subset of hypertensive individuals show reduced Type A behavior with propranolol. Central nervous system mechanisms may be important in producing these effects.